I don't remember finding a guide for it but when I saw the bios menu in the settings, I went "use the source, Luke" way and searched in Lemuroid repo for bios detection.
Here is where it shows the bios files and corresponding systems that you can have and use. You simply drop those files to the same directory as roms. After a scan, you can check and see that bios files you copied are detected. Then it should work with any roms you have in hand for those systems.
Edit: Also I thought I should mention this part as well, copied from Lemuroid help:
*Why aren't my games detected? If your games are compressed, try try putting ROMs into separate directories, one for each system with the following names: nes, snes, md, gb, gbe, gba, n64, sms, psp, nds, gg, atari2600, psx, fbneo, mame2003plus, pce, lynx, atari7800, scd, ngp, ngc, ws, wse, dos, 3ds.
I guess this is a guide now :)