How to notate a held note within a single measure

I am new to MuseScore and am trying to help a friend with a piano piece that is at this point almost illegible. So I am trying to rewrite it so that it incorporates some of her additions and changes for our singing group. I am having trouble with the measures that have a single, held, whole note in the treble clef and alternating rest and quarter notes. Again, all in the same measure. I cannot find anything on this in the manual. Thank you.