Enter the chord edit mode
Create chords like: Cm7, D13, Gsus4, G/B...
Be sure that you are in the "Songwriting" mode of the app.
To enter the chord, edit overlay, double-tap on a chord, in a bar, or in the wheel. Or tap on the "Modal Interchange" icon.
This is the "edit chord" overlay:
If this overlay looks differently:
Make sure your app is up to date (at least version 3.0.3)
Make sure you have selected "Chord" in the lower tabs. Not "Bass note".
Tap the ☑️ icon to save changes.
Tap the ❌ icon to discard changes. This will revert the song to the state it had before you have opened this overlay.