As you can see, the fuse panel is clearly labelled.
The + and - wires from the Univolt are attached to the back of the fuse panel. Not sure if it is a lug type connector. If lugs are used and you can figure out how to mount the fuse panel somewhere where it won't short out. You simply connect the + and - from the 9260 to the fuse panel.
I would drill out the pop rivets on the fuse panel and see what is behind it.
The " charge line" is from the TV and yes it will charge the "house battery" when the TV is connected. But it takes a long time to recharge.
The 2 large lugs on the bottom of the fuse panel with the shunt (copper bar) between them should be connected to the negative side of the circuit. Usually in the house battery negative.
Don't know where the house battery is located in your coach. But I would trace the wires. It should be somewhere close to the old converter. Perhaps with access through an outside hatch like on my Argosy.
If you PM me with an email address. I can send you some drawings and pics of how it should look.
A word of caution. Locate the battery compartment and make sure the cables are not touching the skin or frame of the trailer before you power up the 9260. You can tape the battery leads off for now. As long as you have 120 volt AC power, and the 9260 is powered up. You can run all of the 12 volt
systems in the coach. You will need a house battery for towing to power the breakaway switch as well as any off grid camping.