Does My Camper Really Need a Fuse Box?
Nope! For a small camper, a fuse box is overkill.(Though you do absolutely need fuses -- I personally use inline fuses on the red (+) wires)
But let's say you have a large camper, and you want to set up more permanently-installed wiring using a standard household wiring scheme with a fuse box, outlets, switches and all that. All you have to do is literally PLUG the fuse box into the inverter (by adding a plug to the end of your entrance cable). That's all. Then you just run your standard NM cable from the fuse box to your outlets and switches and fixtures the "normal" way you'll learn in any book on home improvement.However, I really think that standard wiring is completely unnecessary for a small truck bed camper. If that's what you're used to, then go for it! But if you're a relative beginner, it's a lot easier to understand what you're doing if you start simple, stringing around loops by hand, so you can see where the electricity flows without trying to design an electrician's schematic.
Just remember -- especially if you're a beginner -- electricity can kill! Your huge battery can deliver a lot of juice. For a hands-on approach to map out your camper circuitry, I would recommend that you practice using some smaller circuits with a little 12V project battery.
For more info on wiring your own camper electricity, I've posted some excerpts (with diagrams!) from my book at this post:
DIY Truck Camper Electricity Made Easy! (Book Excerpts)