Simultaneous notes of different durations

How can I have two notes of different duration played simultaneously? Whenever I try to add another note, it automatically makes it the same duration as the note that's already there, and trying to change the note duration does nothing. I can technically achieve this using tied notes, but that's not the same. See the images for what I'm trying to do. (If it helps, I'm using MuseScore 2 on a Mac.)