how do you remove the shorts, black top underarmor

i cannot figure out how to do it

You remove/change it from the Body Paint option in the salon/fashion menu.

i tried that but i already have all body paint turned off

If you are a CAST your "naked" look will have under armor UNLESS you equip some innerwear. You need to have innerwear equiped no matter the race or you will see their default "naked" look.