Adding 'Cued Part' notes

Can anyone advise how to add 'Cued Part' notes? eg the often physically smaller-looking notes on music that show as a guide what is being played elsewhere in the band (as a cue..)

When I try adding cued-part notes to a Bar, they overwrite the existing notes that are already there

I did find a thread on this, but I can't figure it out. A beginners step-by-step would be so much appreciated.

Thanks, Corny.