Fëanor tried to avenge his father Finwë's death and the theft of the Silmarils by gathering up a majority of the Noldor and marching to the harbors of Alqualondë to use the ships that lay there. He was denied, and decided to take the ships by force thus commencing The Kinslaying at Alqualondë, which ended with Fëanor killing alot of Teleri Elves and bogarting their ships. He then burned the remaining ships so that Fingolfin couldn't cross with him.
Some sweet maps
I'll try to explain this with maps. Yes, maps. I've found them. Thanks Google.
This is the map of Tolkien's creation made by Karen Wynn Fonstadt:
In the far left, you can see Valinor. If you want to go Beleriand by sea, you have to cross Belegaer and reach Bay of Balar (most optimistic approach).
And this is the map of Beleriand:
It must have been around 19 years (solar years). Too long? Must explain.
In The Silmarillion, there is almost no hint of a passage of time between the departure of the Noldor from Tirion, and their arrival in Middle-earth. The only point where the length of the journey is mentioned is in ch. 9, Of the Flight of the Noldor, where we're told that they had 'marched for a great while in the unmeasured night' (this was after the Darkening of Valinor, so 'night' here just means that they were marching in darkness).
The Noldor set out from the central regions of the World, and a very large number of them had to travel thousands of miles into the far north. It's reasonable to assume that this journey must have taken at least several years.
In fact, we have the Annals of Aman to give us some insight into this matter (in Morgoth's Ring, volume 10 of The History of Middle-earth). There, the departure of the Noldor is dated 1495, and their arrival in Middle-earth is dated 1497. These dates are given in Years of the Trees from their first planting, with each Year of the Trees being equivalent to about 9½ solar years. The Flight ofthe Noldor from Aman into Middle-earth, then, took very roughly nineteen years to complete.
Whether the journey of the Noldor was a 'flight' or a 'return' is a matter of perspective. To the Valar, and the Elves they left behind in Aman, the Noldor were fleeing into the dark east of the World. To the Sindar and other Elves who had remained in the Hither Lands, it was the return of long-sundered kin out of the unknown west.
Also take a look at Shadowy Seas.
Also related: Nienna.
Bonus Information >> The only hint is in Quenta Silmarillion ch. 9, Of the Flight of the Noldor, where she 'cast back her grey hood'. Given that Gandalf was her student, this might (though somewhat doubtfully) have some relevance to his title, the Grey.