If you have ever played any first person shooter on PC then you will know the controls. I think that they are easier than any controller. You can be a lot more accurate with a Keyboard and Mouse.
If you don't like the controls I suppose you could download
this driver and use your PS3 controller.
EDIT: To move around use WASD as arrow keys and the more to look. 1 and 2 are change weapons. Mouse 3 (Clicking the mouse wheel in) or G is to throw a grenade and 4 is to throw a special grenade. F is use, Z is prone, shift is run, C is goto crouch but I use control instead. Oh and Q and E to lean left and right. And of course Left Click is Shoot and Right is aim down the sights.
You can change any of these if you want to.