Use the linemans strap on your safety harness so you have two hands to work with.
So far, for me, messing with pulleys and cherry pickers and elevators has not been necessary.
I just tie the end of a haul line to my belt, the other to the stand which is laying somewhere below (not DIRECTLY below so I fall on it in a failure mode). I place my steps, whatever type I use, and will sometimes use a second strap on step at the level that I will be standing to install the platform, so both feet are on a step. Then install away.
Every stand is different, so practice while on the ground so you know exactly how to do it. Also, see if maybe you need to install from the right side or the left side, depending upon how the straps / buckles are installed (or swap them to the other sides).
ChuckC