I got mine at Pep Boys. It should be available just about anywhere.
Use it like contact cement. Put a layer on the gasket and a layer on the car. Let both tac up and then stick them together. They won't want to move after the initial contact, so be sure to put them where the belong.
Get a heat gun if you don't have one already. It's the only way you will be able to reposition them without ruining them.
I used the 3M weatherstrip adhesive (black). Warning: whatever it gets on, it's on it permanently. Be careful what the wheather strip touches after you put that stuff on it ... it WON'T come back off, though.
That's right -- it was yellow from the factory. Whether you want to go with that or black really depends on the final purpose of the car. I have the yellow, and if you're neat, you will barely ever see it.