Hello! Congrats on your purchase! I just built my pair last week and love them so far, even as temporary mains.
Your kits came with crossover boards, right? You just need to re-bend the leads on each part so that you can stick them through the holes. You didn't say whether you know how to solder or not but just keep in mind that the pads around each hole are fairly large and will need a few seconds of heat from your solder iron in order to allow the solder to flow evenly/nicely/thoroughly. Beyond that, just use some hot glue around each component when your done just to insure that nothing is going anywhere. As far as what part goes where, you can check out the photo on the product page on the DIY SG site for reference.
For the cabinets, are you building ported or sealed? If ported, you can just line the walls on the inside with insulation of your choice. I'm personally going to use the denim insulation that Home Depot sells which will be itch free. You can always use the pink stuff but either way, keep it away from the ports.
If you're building sealed, just stuff them with a fair amount of polyfil and call it good.
You'll need some way to affix the crossover boards to the insides of the cabinets; just something to think about.
You can check out my Volt 10 build as well.
Good luck and snap a few photos along your way!