Chord Notes help

Hi, so, I'm doing a song in 3/4 timing. Anyways, I want to make a chord with a dotted half note on the bottom and 3 quarter notes on the top. It won't let me, though. Whenever I try to make the bottom note into a dotted half note, it makes the note above it on the chord also a dotted half note. Also, I'm only using 1 staff, if that helps. Please help me, I won't be able to progress in my song without this. It's in the second to last measure right now. How do I fix it and make it how I want?