Someone help! I cannot figure out how to get the spare tire off my mom's 2001 Isuzu Rodeo LS!

If it's mounted underneath the truck, there is a crank that will lower it via a chain.

Lift up the rear passenger seat, and get the tools to do this.

Place the two long bars together. One of them will have a circle on the
end. Slide these bars in the hole just above the rear bumper. The
circle will fit in a slot on the crank, above the spare tire. Put the
tire tool on the end of the long bars and turn the crank. The spare
tire should start to lower. You put it back the same way.

Hope this helps.