1. there is a 10mm plastic cover on a 8mm bolt on the inside of the fender, and the quarter panel. the plastic part will most likely break off and you'll just loosen or break off the 8mm depending on how rusty it is. that little bolt is holding the trim piece on the car.
2. once you remove both the trim pieces open your door and unscrew the black door trim. 2 screws on both ends.
3. take that off and just put the side skirt in its place. re use the 2 screws on the inside of the door trim and snap everything else in with the clips.
4. (optional) drill holes in the bottom of the car and thread some screws with washers through the holes in the bottom of the skirts. i didn't do it, they haven't fallen off in 2 months.
if you have 97+ outer door trims, there are 2 8mm bolts again holding those onto the door. or maybe 1 i don't remember, but just unscrew those and slap the 97+ trims on the doors. sorry don't have pictures, but it's super simple, i did it with no instructions on one side and let my 12 year old brother do the other side.