It appears you can use any regular powered subwoofer with the unit. It's a piece of cake.
On the back of your unit, the bottom right has a jack labeled "sub out".
Run an rca/rca interconnect from that to the input on the sub
I don't think that promedia sub will work. That's part of an integrated system and isn't made to be used standalone.
check your soundbars instructions for specifics but, in a nutshell, your sub will have a level control and a crossover control. Set the level to how you want it and use the crossover as your ears dictate.
Enjoy.