Separate notes on the same staff

Hi all,
I am new to MuseScore and would like to know how to separate notes on the same staff. The type of music that I need this for is the barbershop style (four males or four females singing a-capella). I have attached a short "tag" to show what I need to do. The tenor and lead parts are on the treble clef staff and the baritone and bass on the bass clef staff. They have to be separate with the stems pointing in the opposite direction. I understand I could always create four separate staffs, but when the score is printed, just two staves with all four singing parts shown is what is needed. Any help would be greatly appreciated.

Thanks in advanced,

Ron Davidson
Mt. Sidney, VA