1999 Cadillac Catera Oil Filter

This car has a 300 V6 engine with a 2 peice canaster oil filter (dumb) I want to start changing the oil myself. The canister has 2 pieces and an "O" RING (suplied with each new filter) that goes on the top or near the top between the 2 pieces. The top piece or the cap has 4 rings/slots. Which one would the "O" RING go in? The one closest to the end so when you put the pieces together it would form a seal between the two or in the 2nd ring? The problem I have been having is when I would take it to get the oil changed they don't always get it sealed and I end up with an oil leak. So instead of paying $50.00 to get a leak I 'll do it myself.