I was trying to type more and edit the reply because it looked rude after I submitted it.

The threaded holes in the cap should have an external fitting with a line going to the pump inlet, and an internal fitting with a clunk line going to the bottom of the jug or can.

The line from the pump outlet connects to the nozzle that has the o-rings. This nozzle goes in the other opening in the cap to seal the system when you're not filling or draining your tank.

I pulled the photos from Chief's site becasuse the "sort of" show the assembly.