My receiver has two subwoofer outputs... How do I connect the subwoofer?
Always check the manual, but typically you can use either when there Dual Sub Outs
When a receiver has dual subwoofer outputs the two are typically duplicates of each other with a common internal connection. You are therefore free to choose whichever is most convenient.
If they are independent, and you have only one subwoofer, then simply choose one of them and indicate in the receiver setup which one you have chosen to use.