Using the mouse to add notes to chords

Hi -

The handbook says, "During note entry, MuseScore automatically advances in the score. If you want to add a chord note to your previous entry, hold down Shift and enter a note name: C D Shift+F Shift+A E F

How can I add notes to my chords using the mouse to enter notes? I think in terms of the lines and spaces on the staff, and using the keyboard to enter notes is very painful for me to do.

Thanks,

Fifist