Hi Scooter,
Herbert is a long-time user of Notation Composer, and therefore knows a lot of things that may not be obvious to a new user, and which a new user may find helpful. I do that myself
Notation Composer is quite feature-rich, but with a fairly clean interface, so it's not all out there overwhelming you with all the goodness under the hood, so to speak.
To get a single staff for creating a Fakebook Lead Sheet, you can:
1. Use the Staff/Merge command and merge the two staves that have the notes you want for the lead sheet.
2. (Optional if you want to differentiate the two singers/voices). After you've merged the two staves to get all the notes on one staff, then go through and select the notes (you can click-drag across multiple notes at a time), and then choose one of the vocalists to be "Upper voice" and the other one to be "Lower voice". You'll find those buttons to the far right on the Notes and Rests/Notes tool palette.
At this stage you can add lyrics (typical for a Fakebook Lead Sheet) if you want.
3. Now you can run Part/Prepare Fakebook Lead Sheet, and select the merged staff you created above as the Melody staff.
Enjoy!
Sherry