notation in musescore

Hi There! I am a newbie with muse score and am trying to arrange something. However, I am having difficulty figuring out how to put two different rhythms together (ie a doted half note with 3 repeated quarter notes) on the base line in the grand staff. I know it has to be something simple, but since I have not been using this long, I would like to know how to do this without having to look through everything to find it. I can have two different rhythms in the treble and bass line, but cannot figure out how to do two different rhythms on the same bass line. Thanks!!!!