Next, you need to sign your VBA code project in the VBA IDE by going to the Tools menu > Digital Signature... and pressing "Choose" to choose the certificate you created above.
So far, this is relatively straightforward. The problems come when you're trying to re-install certificates after an OS re-install. Or trying to install certificates on someone else's machine. Here are some clues I've found:
1. The actual certificate files are stored in %APPDATA%MicrosoftSystemCertificatesMy
2. There's a snap-in called Certmgr.msc which helps you manage certificates. You want to drag your self-signed certificate into the Trust Root Certification Authorities > Certificates folder.
3. When you open a MS Office file that has signed code in it, you want to try to "View Certificate" and "Install Certificate" if you can. Or "Always Trust Macros From This Publisher". Here is a good link on some resources to help you.
I'll continue to be on the lookout for more information about backing up and restoring certificates before and after a machine reinstall.