Okay so my camera is busted right now but you have the primary terminal up top. It has 3 connections: left, center, and right. You also have a secondary terminal, the two leads that head out towards each plug, left and right.
Set your meter to ohms. touch one terminal to the top left primary connection and the left side secondary. next one top right primary terminal and the right side secondary. that is how you test the secondary.
Then for the primary, touch one end of your meter to the center primary terminal and the left primary terminal for the left side, next again touch the center primary and right primary for the right side.