Well, the basic process of setting it up for use is the same for all platforms, the only difference being the way inputs work in the settings menu (stuff like button swaps(A/B vs Cross/Circle vs Enter/Escape (although this can still be used using the OSK (except for the PSP build, which doesn't have a touch screen nor a mouse to use it) or physical PC-compatible keyboard))).
Although usually the XT doesn't need much more than the ROMs (and required floppy/CD-ROM images to actually boot it). Although MIDI emulation on non-WIndows platforms requires a soundfont (sf2) as well.
The remainder after placing the ROMs in their correct locations is the setting up of the emulator itself (which can be done entirely from the settings menu when opening it during startup of the emulator).
It already mentions all basic steps required to get the emulated machine booting properly. Is there something missing?
I've added some extra information here and there on the machine specific parts and an explanation of some required i430fx/i440fx settings to set inside the BIOS menus when pressing delete during the POST. It's the same with the real machines, but that's got nothing to do with UniPCemu itself (the exact same is true with other emulators like qemu etc.).
I went through my PMs and invited everyone who was interested in my Rock Band Customs Project to my new group (14 people!); if anyone reading this has an invite from me, you're not obligated to accept (but I'm hoping you will).