I figured it out. If anyone stumbles across this in the future. You need the WAV file of the BASIC program. Select the bin for BASIC version you want to use and press the utility menu (4). "Set as BASIC"... then when you try to load a WAV, BASIC will boot. Load as if you were loading a tape.
If you do not have the overlay, press . (that is, press period the screen will change color), press + (a colon will appear on screen), press = (screen will change color), press 2 (the word INPUT will appear on screen), then press C. If you have the right version of BASIC, the WAV should load.