Wheres he exit?

First grey rectangle in the left of the combat space, a spot in the middle (not on the edges of the rectangle)... but I think you already found it by now...

I cant select a vessel
How can i get to the mainland?

If it isn't docked, you can't really enter

You'll see there's a vessel x light years away from you. Check in from time to time (a few minutes) and you should see it arrives in 10,9,... minutes. Then, once it's docked, it will wait you to board it for 10 minutes. Do so, and when the voyage starts, you can see the ETA on the ship's viewscreen.

I will be finishing the viewscreen so it explains what the ships are doing in more details