Add it to your neogeo.zip or set it as the primary bios in settings.
First, forget everything you know about cartridge-based consoles. The Neo Geo AES (Home Cartridge) had a simple BIOS. The Neo Geo CD, released in 1994, was a different beast. neo.emu bios
One cool trick only possible via the BIOS in NEO.EMU: Add it to your neogeo
Neo.emu BIOS: The Ultimate Guide to Running Neo Geo on Android released in 1994