International priority will have 2 pages total 4 half pieces. 3 of them go in a clear pouch, available at the post office, and one is yours to keep. Sign them all.
Yes, the PO will give you the pouch for them to go into. They should have them available at the counter and if you ship priority international often you can order them for free online or just ask the clerk at the PO for a few extra to take home with you.