Using a tacometer to work with pc games to show the revs of the car

Hi im thinking of buying a ceap tacometer and using it to show my revs in the game on the tacometer. But the problem is that i have no idea how to do it i have watched alot of youtube videos but non of them really explains how to do it. So can some one please let me know how to do it and not too complicated i am a noob when it comes to programming arudino etc. ;)