Depends on what kind of car. The jist of it is your gonna have to take the tranny out, away from the engine, and unbolt the clutch plate from the flywheel. Then installation is the reverse of the disassebly. If it's a FWD it can be tricky getting out the transaxle, but a RWD car is alot better to do. There are a lot more details and stuff to look for, but that's the meat of the proccess.
Get a manual and a torque wrench... Remember to replace both the pilot and throwout bearings, it'll suck to replace the friction material and have to tear it apart a little later due to a bad bearing.