If you read my earlier post, you know I had a short in my running lights. Thank you for all the suggestions. So to answer my question on how you find it.
First, you go buy a voltmeter / continuity deal. When you get home, you open it and read the instructions, only to realize that you really know absolutely NOTHING about electricity, be it AC or DC. So you spend half an hour on google, to find out that even google can’t fix stupidity. I did figure out how to get it set to check continuity, but all it would do was make this loud noise, and show zero. Come to find out later, that was the important part. We’ll come back to that.
On to suggestion two. I got out my battery charger and was going to try hooking that up to the lights to see if I could figure anything out that way. Then I said to myself, Self, you don’t know anything about electricity, so this may not be your best idea of the day. Scrapped that idea too.
On to suggestion three. I pulled all the lights off except the two on the tongue and the one on the back of the trailer under the keel. The ones on the tongue were screwed to the frame and sealed, so I left those, and I forgot about the one on the back. I went around with the voltmeter and again, all it kept doing was buzzing at every connection.
On to the next suggestion. Changed the fuse in the truck and hooked up the lights. The ones on the tongue turned on just fine and no fuse issues. Hooked up the rest of the side lights on each side one at a time, and they all lit up and stayed on, even though they did seem a little dim. Hooked up the left tail light, still working. Hooked up the right one and it worked fine. Noticed one ground wire I forgot to hook up to the light (there were three that were connected to the bolts that attached the light), which must have been for the center light as that one was still out. Took the tail light back off, hooked up the ground, POW, out goes the fuse.
Took the center light off and low and behold, when I pulled the wires out of the frame there was a bare spot on the brown wire. I pulled that segment, put new wire from the tail light to the back light, soddered it, sealed all the connections with liquid electrical tape, three times, problem solved.
Went back to the pigtail after fixing the short, and low and behold, no more buzzing on the voltmeter. Go figure. Had I known what the H*%# I was doing, I would have figured out the short was in the center light when the tail light connection buzzed since the only light further down the string was the center one. Since I misunderstood how the continuity part worked, I didn’t realize that was what it meant.
I did learn a lot though. 
Sometimes, its tough being an idiot.
It only cost me 12 1/2 years of student loans to figure that one out 
