Help Installing 12 Volt Outlets

Twelve volt electrical newbie here.  I need to install some outlets in the 176.  I want to make sure I'm doing it correctly.  These will mainly be used for charging cell phones and other such devices (which also makes me wonder whether I need to change out fuses for higher amps).  There are three areas that I would like to place them.  I do have dual batteries.

One is right next to the bunks, which I believe I have figured out since the converter is right there.  I plan to run new positive wiring straight into one of the unused slots, and the ground to the grounding block screwed to the floor.  Probably use a 15 amp fuse.  Sound about right?

The other two are the ones I need more assistance with as I have read to just use existing wiring.  Which wires do I need to tap into, and how?  I am planning to use Scotch Locks unless there is another way.  I have attached pictures and would appreciate someone telling me which wires to tap into.

Near the tv.  On the 176, this is the wall on the left as you enter the trailer.  Trying to tap into the antenna power for an inverter.  Would it be the two wires with the capped connectors?  The one in front of my hand and the other connected to the blue wire in the background?

And in the rear of the trailer, on the right as you face the back.  This is where the heater and hot water are located.  Too much for a novice like me to figure out.  Which wires do I tap into?

I have more pictures if necessary.

And any other input is greatly appreciated.  Thanks in advance.  This forum has been a lifesaver.