I own a 1997 Pontiac Bonneville, and my driver/left wiper arm sweeps past the windshield frame. How I can I adjust it so that it stops before the edge of the windshield?

How is the right/passenger arm? If it is only the left you should be able to pull it off and readjust it.

It will be trial and error.
What I find best to do is, turn power on(don't need engine running) with right hand on key, and left hand on wiper switch, advance it one click, once it gets to the end(before it comes back) shut the power off. Remove wiper arm, reposition to where it should stop, and do a test sweep. If necessary, repeat until you get the wiper where you want it.