Stems are created by pressing + (plus) or - (minus) followed by a duration value. Possible duration values are 4, 8, 1, 3 and 6. When creating stems, the stem will go up from the cursor position if the - key is pressed, and down if + is pressed. For example, to put an upward sixteenth note stem and flag on a notehead, put the cursor over the notehead, press - and then press 1. To put a downward eighth note stem and flag on a notehead, put the cursor over the note, press + and then 8.
It is also possible to beam single notes the same way you beam a group
of notes, that is by selecting the note to be beamed by dragging the mouse
over it and then selecting Beam from the Edit menu.
Adjust notes within a beamed group