Im going through my electrical system trying to find a short and found something odd. On the fuse box on the top left below where the blinker thing goes in there is a terminal marked acc (or something like that). The odd thing is there is only one terminal there??? I looked where I think the other should be but there is no terminal. In fact it doesnt look like there was ever one there. Any thoughts?

Most fuse boxes do have a few extra terminals marked "ACC"/accessory. Some are used for optional, factory equipment(like a map light), some are just there in case you wanna add something, like fog lights, or a tape deck(8-track, of cours..LOL!). An "ACC" terminal is not usually hot all the time, it may only be hot with the key on. Terminals that ARE hot all the time are normally marked "BATT".

Well after messing with it all day yesterday and doing some reading it seems there should be a terminal in ther last slot for a circuit breaker for my power windows. So next step is to remove the fuse box. I know there are 2 screws that hold it on but how do you take it out? It seems to be held on by all the wiring???

Not sure when they changed it, but the p/w circuit breaker for my '74 is under the hood, on the firewall.

The fuse box is held on by a single bolt from the engine side, where the harness goes thru, under the brake master cyl/power booster. It's a 3/8" bolt, if I remember correctly. Once this bolt is loosened, the fuse box can be pulled away from the firewall from the inside. Don't expect it to just fall off tho...
Your's may have a couple of screws on the inside too, holding it to the firewall, but I don't recall ever seeing one like that....but I haven't had the pleasure of standing on my head under the dash of many '76s!
hth