How to add harmonica tablature using the plugin.

Help please. I'm trying to record simple harmonica licks. I'm using MuseScore 3 and also have MS 4 available. I want a normal 5-line stave with notes, and then have the corresponding blow and draw notation underneath, e.g. "-2" for G (example image attached). I'm only a beginner player and fairly new to MuseScore. I've managed to load a harmonica tablature plug in, and have a score started. I've selected 10 Hole C Diatonic Harmonic as the instrument. I can add notes to the stave, but the harmonica notation doesn't magically appear. Can someone explain please? How do I know if the plug-in is activated? It has a tick in the plugin manager. How do I invoke it?
Cheers, Rob.