Here are instructions for arriving at what you see above:
1) in the partbox, select a note that has a [i]smaller[/i] rhythmic value than the value you want to see in the tuplet. As you can see here, my goal was to create a 5:4 quarter note tuplet, so I started off by selecting an 8th note
2) enter that note on the downbeat of where you want the tuplet to start
3) select the tuplet "tool", represented by the -[i]n[/i]- symbol in the partbox, and drag it on top of the note you just placed in the score
4) a tuplet dialog box will appear. I then configured it as shown:
5) Hit OK on the dialog box. What you will now see in the score is a quarter note followed by 4 quarter rests (not shown). Drag notes from the part box to each of those rests.
If necessary, adjust the pitch and length of the notes as necessary, either right there in the score editor, or, in the piano roll or event list.
This procedure will work for any type of tuplet, including duplets.