Hi guys. I downloaded a pack of MAME 0.240 ROMs, added the ROMs as a Complete MAME ROM Pack, but Retroarch didn't show up as the default emulator option. So, I went to manage emulators, Retroarch, edit, and added Arcade in associated platforms. However, even after changing the core to some related to MAME, the games don't open. Is the problem related to missing BIOS files or how do I solve this?