I actually just got a response back from the Apple guru guy at Apple and wanted to share with you what he said... and also even when I try to follow this later, I still may need this broken down, I'm not sure till I get the program open in front of me. I'm sure this will be cake for you though-
You got the Pen Stroke Tool (P) correct! :)
1. The first *trick* is to open either the HUD or the Inspector BEFORE you begin writing. In either the HUD or the Inspector>Behaviors, make sure Write On is checked.
2. The second *trick* is after you have written the signature is go ONLY to the Inspector to make changes. Making changes in the HUD will no longer affect anything already written. Make any changes to the look of your stroke under Inspector>Shape>Style. Whereas by look I mean the thickness, what colors, roundness, etc.
3. To manage the life of the stroke, or in other words to keep the stroke on the screen from going away, brings us to the third *trick* which is go to Inspector>Shape>Advanced and make sure Dynamics is turned ON. There, you can adjust the life. And you will want to do that because otherwise lightstrokes like to go away after a brief moment--which is NOT what you want.
Hope that helps!