Hi, since you have the drum off,you can loosen the adjustment from the front side. I am sending a picture and the instructions. It tells you to us a brake gage, sending a picture of one. You can do the adjustment without it,by loosening the adjustment so the drum slides on,remove the drum, open the adjuster until it has a slight drag when the drum is installed.
Where is the automatic adjusting lever and adjusting screw labeled on that exploded view of that drawing? I take it these brakes are automatic adjusting because while I was waiting I stepped on the brake pedal to see what the brakes would do, thinking they would expand and contract, but instead they expanded and didn't contract, because I didn't have the drum on? If it is labled #8, do I need a special tool for that?
If the shoe didn't contract,make sure the shoe is in the slots on brake adjuster ,and that the wheel cyinder is not frozen, you should be able to push both pistons in equally.