This is the first thing that popped up using
this Google search. Haven't tried it out myself since I just use my brother's USB X360 controller when I feel like using a console controller for certain games.
But I totally recommend familiarizing yourself with the mouse and keyboard. There is a reason a lot of PC gamers are elitists when it comes to FPS games. Key thing though: Don't be afraid to go into the game options and tweak the sensitivity until you find something you're comfortable with. Personally I crank my mouse sensitivity pretty high, but I know a few people who prefer to have it lower, so keep changing it until you find what feels right.