How do I activate new characters?

You can find a wealth of information in: FontCreator - Tutorials and Solutions

Circle Secrets is a good introduction to the basics.

The Bounding Box is a concept that needs to be understood.

Insert Characters will help you.

How Do You Adjust the Cap Height and x-height Lines? is good information.

Sample: great tool for Spies & Secret Codes Is another way of inserting glyphs.

I hope you enjoy this learning experience as much as I have!