add notes?

I am very new to using MuseScore.
I have been fairly successful in using this but have a question of how to insert extra notes in a measure. I will show a picture below of what I need help with.
I have a dotted half note and 2 quarter notes, but need to figure out how to add the whole note below.
Image 4599 what I need it to look like
Image 4600 what I have been able to add in MuseScore
Thanks for your help.