If you go to the tie-in page Board the Endurance (which can also be found at the link Valorum gave) and click on the module labeled "main engine module", you get the following image (click to enlarge), showing that four of the modules are actually engine modules which presumably contain fuel:
The text reads:
The Endurance's engines feature advanced magnetoplasma rockets, which produce a distinctive blue exhaust plume of ionised gas when firing. Each module contains a compact tokamak power plant which generates electricity via magnetically-confined fusion. As well as generating electricity for use in the engines the tokamaks supply power to the rest of the Endurance's systems. Each engine module features small manoeuvring thrusters on its corners. These are standard hydrazine thrusters of the type use in present day space travel.
So the maneuvering thrusters (which would be used for things like changing orientation, spin, and docking maneuvers) are chemical rockets using hydrazine, the main thrusters (the three circles seen in the diagram) are magnetoplasma rockets, also known as ion engines or ion thrusters because they use magnetic fields to accelerate a plasma of charged ions which serve as propellant. Perhaps it would be similar to the proposed VASIMR (Variable Specific Impulse Magnetoplasma Rocket), a proposed type of ion engine which would be much more powerful than any of the ones currently used on space probes. This type of engine creates less thrust than chemical rockets (i.e. it accelerates the rocket more weakly) so it can't be used for takeoff from a planet, only for travel when the ship has already achieved escape or orbital velocities. But the advantage is that because it would have a much higher exhaust velocity (30,000-120,000 meters per second according to the table here, compared with 4,400 m/s for the best chemical rocket), according to the Tsiolkovsky rocket equation this means it can achieve a given delta-v (change in velocity over an extended period of time) using much less fuel mass.
As mentioned in this article, in the section "Webster, We Have a Problem", VASIMR would probably require nuclear power to generate the needed electricity for long-term spaceflight, so that may explain the reference to nuclear fusion above (unless they're suggesting the superheated plasma from the tokamak reactor is used more directly to superheat and ionize some exhaust as in the proposed fusion-driven rocket of the kind outlined in some NASA presentations here and here, but when they say the tokamak is used for "generating electricity for use in the engines", it sounds like the engines themselves don't rely on nuclear reactions for anything but electrical power). An article here has a quote from the movie's visual effects supervisor Paul Franklin which confirms it's a type of ion engine: "The engines are imagined to be something plasma electric, a super-advanced version of the ion engines already being used in space exploration. But of course, these [film engines] produce much, much higher levels of thrust than the ion engines of today. So the engine pods would have some kind of compact tokamak [nuclear] fusion generator for power, that sort of thing."
As for the Ranger, that can also be clicked on the Board the Endurance webpage, giving this screen:
The text reads:
This is a fast, agile reconnaissance vehicle with single-stage surface-to-orbit capability. It can also be launched in a double "belly to belly" configuration on top of a large multi-stage booster. The Ranger can carry a crew of four people and one robot. Each ranger has its own cryo-sleep tanks for long duration missions. The Ranger is driven by a combination of chemical rockets and plasma jets. Hydrazine thrusters are used for maneuvers in space.
The Ranger was probably inspired by the VentureStar, a real proposal by NASA for single-stage vehicle that could take off from the ground and achieve orbit (with the fuel carried in internal tanks), whose shape resembled the Ranger:
And here's a picture of the proposed Lockheed-Martin X-33, which was to be a 1/3 scale prototype:
Since your question was about where fuel is stored, page 8 of this report to Congress shows a cutaway of X-33, showing that its body is pretty much devoted entirely to fuel tanks; presumably that's just because it was intended as a prototype, and the larger VentureStar would have had room for human crew, but I'd imagine fuel would still take up the majority of the space onboard.
VentureStar would have been able to achieve orbit without boosters using an improved engine design known as the Aerospike, described on the wikipedia page:
The aerospike engine is a type of rocket engine that maintains its aerodynamic efficiency across a wide range of altitudes. It belongs to the class of altitude compensating nozzle engines. A vehicle with an aerospike engine uses 25–30% less fuel at low altitudes, where most missions have the greatest need for thrust. Aerospike engines have been studied for a number of years and are the baseline engines for many single-stage-to-orbit (SSTO) designs and were also a strong contender for the Space Shuttle Main Engine.
A blog post on a visit to the Endurance prop here notes:
Other than its slightly fanciful shape, Ranger looks utterly authentic - as if it just landed. I can't really glean too much from the spacecraft's operation except to note that it seems to have something like aerospike engines.
Here is a page from another person who went to visit the prop which has a photo:
The two exhaust ports each have a central fin sticking out which looks similar to the "tapered nozzle ramp" on an aerospike (used to direct exhaust flow and increase efficiency) seen in the diagram here:
So I would say the combination of the similarity of the Ranger to the VentureStar and the fins seen in the prop make a good case that they were intended to be aerospike engines, though I'm not sure if this has been officially confirmed. The article here claims that "These ships, according to the producers, use an aerospike engine", but I can't really sure if the article's author actually heard this directly from producers or just saw aerospike engines mentioned on the Interstellar wiki page (or something similar) and assumed without checking that the information must have come from people involved in the film.
Also note that while the Ranger needs enough fuel to achieve escape velocity from planets, The Science of Interstellar by physicist Kip Thorne (who consulted on the movie) indicates that once away from planets, most of the maneuvering is supposed to have been done by gravitational slingshots around "intermediate-mass black holes" that orbit Gargantua (the supermassive black hole seen in the movie). See my answer here for details.