Replacing content of measure

I am very new, not a musician and very old, a nonagenarian (90s). Have searched the documentation but unable to solve my problem. I have tried several ways to correct the notation in one particular measure. In trying to edit the measure and correct the error I made I have made the situation worse. Final thought was to delete the measure and try to insert a new one in place thereof. No luck in any of my attempts thus far.

Key of F; 3/4 Time; The measure should read: dotted quarter note on A, one-eighth note on G, quarter note on G.,

I entered a dotted quarter note as the first entry. Then I mistakenly entered a quarter note. Before realizing my error, I clicked on the G line for what I anticipated would be the final quarter note in the measure and an eightieth note was entered and tied to the next measure.

That's when I really began to mess it up. The score is complete (Just a hymn that I copied from a hymnal which I had hoped I could transpose to another key in Musescore) except for that one measure.

There is a very short line above the measure. When I try to enter notes in the measure, as soon as I insert the first dotted quarter note the cursor (blue box) moves to the next measure. Since that note is note a 3 beat note I can't figure out how to fix the measure properly. Any help would be appreciated.

oldmac