Pioneer avh 4200 and powered sub

Hey there folks. I have what is probably a very stupid question. I have an avh 4200 and I want to add a powered sub. The back panel has sub out l & r. The powered sub has 2 RCA plugs. My question is probably obvious by now. Do I use a split RCA on the l or r RCA, or do I use both l & r sub outs? I have let the smoke out of stereo equipment in my younger days, so I want to be sure...
Yes, I posted this before, but I guess it was in the wrong forum. Who the hell knows....

 

Are you intending to drive the sub without an amp? If so, you're going to be disappointed. If with an amp, run both L and R to the amp and make adjustments on the amp to send a mono signal to the amp. Should be dip switch or rotary switch.

 

Isnt the point of a powered sub to not have to have a separate amp? I am looking at something similar to this: