how do i add custom music to 3ds theme

im using usagi editor and i have the bgm but the button to add bgm is grey and i cant click it
i already enabled bgm in flags
HELP

I have absolutely no idea. I know how to do it on Switch, but not on 3DS. @Roxas_971 might know or I might be able to figure it out.

Someone summoned me ?

I've never used usagi but :
-the songs must be in bsctm or somethin like that, it can't play on mp3
-I think the maximum file size should be below 5MB, I don't remember anymore

Or, check this instead :
https://gbatemp.net/threads/help-how-to-add-bgm-to-usagi.588179/