I would just hook up the two large cable first. i think i am reading they are large size cables one is black and one is white...
Hand trace the WHITE cable first and it should go to the trailer frame ground. This will be your NEGATIVE 12VDC cable. Mark it with something as -12VDC...
The other LARGE BLACK cable will be your POSITIVE 12VDC cable coming from the Power Distribution Panel where you converter hooks up to it. Mark this one + 12VDC.
You will need to trace out the other wires and find the pair of wires coming from some other appliance or device.
The normal wire colors are Black for positive and White for frame ground. But as I said earlier two worlds are at play here being the RV TRAILER world and the AUTOMOTIVE WORLD on which wire colors are used. If can find the pairs coming from a device or appliance they may be BLACK and WHITE wires going together or RED and BLACK wires going together.
This gets alot folks into trouble when wiring back up haha...
As for as solar goes a good starting plan is to install 120WATTS of solar panel along with their solar charge boards which will need to connect to a battery system.
A good choice of affordable batteries is to get the two GC2 GOLF CART 6VDC batteries from SAMs CLUB or COSTCO. You need somewhere for the solar power to go to have it available when you need to use it...
The two 6VDC Golf Cart Batteries will have around 220AHs capacity and would be a great battery system to go with a 120WATT Solar system.
here is a quick wiring diagram on how to connect up the 6VDC batteries in series or the 12VDC batteries in parallel.

Here is a quick 30AMP Electrical flow diagram that might be interesting for you showing a typical electrical setup for the RV Trailer.

There are lots of little things to learn here and it would be great if you had someone close by that is aware of how all of this works to get you started in the right direction.
ALot is lost in trying to pass along this much info over forums like this. Everyone has their own way of describing things (myself included) haha
Roy Ken