So go to Thule or Yakima websites. They'll have a way for you to look up the right fit kit for your car. You'll have to put in your make model and year. Once you know what you are looking for then you can go to Craigslist and narrow your search. Fit kits fit different cars.
You need the "cleats" or or "feet" that attach to your car's roof/door top. Then you will need a couple of bars. You can buy whatever length of bars your want. Just know if you get them really long you'll give yourself and your friends concussions getting in and out of your car.
Once you have those, the last thing you'll need are a couple of cam straps to tie the boat down.
If you buy the roof rack brand new (from REI or whatever) they usually come with a couple. Otherwise head over to NRS or your local boat shop and pick up some.
I'd recommend a couple of 15' with the protective bumpers. You can tie your boat down with one 15', as soon as you take a friend you'll need two.
You ARE a soul, you HAVE a body.