I don't know the words to ask this question

I don't know any of the words to ask this question. I'm trying to type in the notes for the attached measure into Musescore, but I don't know how to do it. All I can do is make all the notes the same length. How do I make the bottom notes in the measure independent of the top notes? Is there a tutorial video that I couldn't find that teaches how to do this? Thanks!