How to erase a note

Welcome! Click it-> Del

Or select the note, then right click->delete (or via menu edit->delete)

Or, if you want another note instead, select (click) it then overwrite by typing an A - G.
See:
https://musescore.org/en/handbook/note-input#basic-note-entry

Erasing it or deleting it will leave a rest.

And if you actually want to not just get rid of the note but actually want some (unspecified) number of subsequent notes to move earlier in time, then don't bother erasing the note - just select the notes you want moved (only you can possibly know how many) then cut and paste them to the new location.