how do l install the driver side door window lifts on a pontiac grand am GT?

Just take off the side panel and you will see what you got to do.

Once u take off the door panel remove the weather coating & then if window is almost down fully if u look inside u should see 2 screws that r on a metal arm that is connected to the bottom of the windows glass.. Trick is getting the window out through the door but if u lift up on on a angel u will get it out. Then reverse the process & u minus well lube the windows tracks while at it.Plus clean any plug in connectors contacts bec in time the weather causes them to corrode especially a car of ur age could use it.
Hope this helps u & best of luck

Um, sell the car!
Hopefully u r talking about only the motor. Once u have the door panel removed u will see a few cables running to the window & 2 pulleys from a central hub. The motor is mounted with 3 bolts or rivets ( l cant remember). Remove the motor, put the new one in & plug it back in. Reinstall the switch block to test the system before u put the door panel back on.
If u need to replace the whole regulator asssembly buy some red bull, it is going to be a long night. Before u start buy the regulator (the hub looking thing that has new cables running out of it, a new motor & the white plastic clips that attach the glass to the pulleys. If the regulator is shot buy a new motor & clips; it is not worth trying to save them.
Once u have the door panel off take a few pictures to help u put it back together right. Put a piece of wood inside the door to block up the glass. Disconnect the clips that r attached to the glass & lower the glass onto the wood after u unplug the motor. There r 2 vertical pieces of metal to which the whole window system attaches. You need to unbolt them! You can not work on the cable system with it inside the door. There should be a bolt at the top & bottom of each support, remove them. Carefully take the whole assembly out of the door & set it on ur work bench. Take a bunch more pictures. Lay the new parts next to the old ones. As u remove one pulley or part from the frame replace it with the new part. Do NOT take all of the pulleys out then try to remeber where they go! Installation is the reverse just make sure u use new clips on the glass. It is useful to have an assistant around when u put it back together.
Good luck