Hope you can guide me through this.  Everything else is very clear, well written and designed.

Have you watched the quickstart videos (there are two on tuplet entry) or read the Quick Reference Guide (linked in the Help menu)?

Here's a tutorial I wrote a few years ago. Many people have found it helpful.

http://www.specialmillwork.com/finale-tips-and-tricks/tuplets-with-simple-entry-2.pdf