how do you release the pressure on a rear brake cylinder on a 99 chevy tracker on 1999 Chevrolet Tracker

i made the mistake of pumping the brake pedal with the drum off ,now i cant get the drum back on.

you may have to repl wheel cyl, then tend to leak after this happens
Also check the parking brake adjustment . If it's a self-adjusting parking brake you will need to find out the method to reset it or it will still be difficult to install drums
1 more answer
Loosen the brake line at the wheel cylinder. Make sure you have something to catch the expelled fluid. Tighten the line after you push the shoess together. Goodluck