If your controller is wireless, you'll need to install drivers for it. If not when you plug it in it should work. You need to open up the game you want to use it with it and go to the control settings.
check in the controlers menu. i think it will be the last 1 you can select if its being seen.
if its a direct input device it may not work. look for the 360 pad emulator and try copying the x-input1_3.dll or 1_8 or 1_9 not sure which 1 it is but 1 of them will force a none native controler to respond like a 360 pad.