Certain emulator cores require specific BIOS files in order to play.
BIOS: ✅ = Required 🔶 = Optional
BIOS files are imported exactly the same as ROMs: Importing ROMs. When you have the correct BIOS successfully imported they will shown in Settings → Cores or they show as missing/red/required, otherwise you have the wrong files. You need the exact ROMs files matching the MD5 hashes above.
Though not required, you can verify the MD5 hashes of your files to be certain. To obtain the MD5 hash of your BIOS files, you can use
md5 [path to file, or drag and drop file here]in Terminal. Check that it matches the MD5 hash of the file listed above.