The XL/XXL Assembly guide is here -
Go to the wiring section. That bag of parts are the brackets for the drag chains. There are no screws included, only double sided tape, so I used a self tapping sheet metal screw to keep mine in place.
You have to remove about 12 links from the chains. Also, don’t try to fish all of the wires through the drag chain. Take off all of the little “doors” so the the chain is open. Get all of your wires run through, then put all of the doors back on.
Use the assembly guide photos as a guide. I’m a little surprised that C3D has still not added the part about removing the doors off the top, as this makes routing the wiring so much easier. But at least there is an XL/XXL assembly guide now.