All caps are very off putting and unprofessional from a sales (or
advice-asking) perspective. You basically set up an account, snap some
photos of what you're selling and make an ad. It's pretty easy to follow
along with.
I think that's a "maker's mark" that is put onto handmade ceramics and
porcelain, often from China. Not sure what that particular one means--it
usually references the person who made it--but it's a place to start
searching. Good luck.
As long as you have Paypal connected with your bank account, it should
all take care of itself, usually in a couple days (if you want it
transferred from Paypal to your account).