The best way to add BIOS files to MAME is to drag updated files from the download folder, and drop them into the ROM folder. However, it is important to keep in mind that MAME is ever-changing and so BIOS files will need to be updated regularly.
MAME is an emulator that allows players to play arcade games on computers. The games require a BIOS file in order to run, and since the creators of MAME are constantly updating the source material, it is not uncommon to find a game no longer works because of outdated BIOS files. Once obtaining the appropriate BIOS files, they need to be added to MAME. The quickest way to do that is to go to the MAME file in the "C" drive and double-click the "MAME" folder. Drag and drop the compressed BIOS file from downloads to the ROM folder in the MAME folder. Start MAME on the computer, and the BIOS files will automatically update for game play.