Oak,
There are 2 plugins on the back of the Axiom sub. As mentioned before, the single output from your receiver can plug into either of these inputs or you can buy a sub cable with a y-splitter and hence plug the cable into both sub inputs.

If you look around ebay, i picked up an RCA brand copper sub cable, 30 footer, for $25.

"Those who preach the myths of audio are ignorant of truth."