Replacement/addition of electrical

The only thing I'm confused about is where my 12 volt fuse panel is in relation to my coverter? In my mind I thought of is as just being a battery charger, but how do I wire it so that it can power the dc circuits without a battery? Is that where the bus bar comes in?

In most typical converter->distribution panel connections there will be a common stud or the (+) phase wires will all be connected together. The converter is wired in parallel with the battery and distribution panel.

If doing a new installation of the converter, I would use a terminal strip or bus bar to connect the 12 V output wire from the converter to the battery wire and the distribution panel wire. This is a pretty critical connection and you want something that won't come loose. If you have the ability to add lugs or ring terminals to the connecting wires, you could bolt them all together. Soldering and covering the connection with a waterproof junction (irrigation splice)is another alternative.

Good luck with the converter!