How to use custom SFX?

I've saved mine in a waveform, but how do I use it?

You're supposed to use it as an instrument for BGM, but if you want to play one as a sound effect, I'd recommend SamKitsune's WAV player library.

To turn a waveform [array] into a usable sound, use WAVSETA. To play that sound, use BGMPLAY"@[sound number][PITCH]