Upgrade from Entune to premium JBL

Hello Tacoma world. I'm not on here much but I was hoping for some help. I have the base, the absolute base model 2016 Tacoma, 4 banger, 5 speed, 4x4. It came with Entune, of course and I'm slowly been upgrading things like the rearview mirror Etc. I didn't see myself doing that but as I'm retired I guess I needed something to do and I've enjoyed each I have enjoyed each addition. So, I can't stand anything on the radio now and thought I'd put in satellite radio. Thanks to Tacoma world I was able to hook up everything I needed. Which takes us to the meat of the problem. I got the GPS antenna and the satellite antenna and the premium Entune w/ satallite receiver, picked up off of eBay for $300, works fine. What I didn't realize is it is a JBL.
So, I successfully cut my dash or reasonably successfully anyway, and installed it. To my everlastings surprise, everything works. Lots of extra functionality, and great sound, well to my ears anyway. I believe I have only one problem, and that is of course there's no volume control and balance doesn't work. I'm not surprised because I didn't realize this was JBL and I know there's problems with that. What I'm hoping for, is someone here who knows something about how I can fix this. There's one more plug in the back of the radio than I have plugs for, so I'm sure it's there. Neither the volume control on the radio nor the volume control on the steering wheel work. As near as I can tell, as I said, everything else works. It plays, but only at a fixed volume. Any (helpful) ideas? Any help enthusiastically appreciated.