John,

You should initially push the project to VSS from VFP, which will create the PJM file in VSS. Then from other machines this is what you select when you join a project. You should make sure you have the PJM marked to allow multiple checkout.

>How to join project that added to VSS using VSS User Interface?
>I have tried to select File->Join project from Source Control, select working directory and source control project, but vfp project listed in dialog box and OK button is disabled. Any ideas?