Q:  How do I use my list of shooters from the official IDPA software?

A:  In the folder in which you've installed ForScore there is a utility program called FSImport.exe.  Run that program and follow the wizard's directions.
The wizard should be able to deal with the original IDPA software version, and the revised version IDPA released to support ESR. If you've modified the IDPA software, the wizard will not work.  If that's the case, contact Beach Bunny Software technical support.