Note input/editing - new user

Can't find the answer to this anywhere so I'll post the newbie question.

If you are entering a two notes on the same beat, how do you separate the 2 notes so you can have different note values? For example high e as half note, low e with quarter note. The program automatically joins the two notes as a couplet and does not seem to allow differentiating them with different note values.

Thanks!