Travel Trailer electrical

Hi thank you for taking the time to help so yes I have a multi meter, and see the fuse panel but the wiring is something else in there. I’ve tried all the wires into the fuse panels but nothing worked. So I unplugged them. I followed the wires from outside and connected frame negative to Meg battery still nothing. I will try multimeter way to see where I’m not getting power. And yes learning is very hard sometimes. I was trying to lean by trial and error but I think I’ve tried almost everything. I will try and post pictures because sometimes I cannot explain what I’m trying to say.