At the end of The Force Awakens, the final pieces of the map to find the planet Luke is on are put together. This leads Rey to the planet Luke is on but that is still an entire planet to search. Luke's home does not appear to be easy to spot with a quick fly over and I would guess he has no beacon set up to lead Rey there, so how does Rey know the exact location of Luke's hide out?
Rey already knew where to go because she'd seen the island chain in her dreams
Those words were still echoing in Rey’s head as she flew the Falcon high above Ahch-To. Rocky islands blanketed with beautiful green trees jutted from the water that covered the planet. Rey recognized the landscape from her dreams. She had imagined the place thousands of times without realizing it was waiting for her. Rey landed the Falcon at the base of the tallest island. A rugged mountain path led from the landing pad to a small clearing near the island’s summit.
And from the film script itself;
so lonely... so afraid to leave... (then, slight smile) At night, desperate to sleep... you imagine an ocean. I see it -- I see the island...