The import into Vault is a one-time migration task. You can't really add to the history in Vault with that tool.
What you can do now is open Vault, perform a check out of the files you made changes to (not the same place where you keep VSS files), then close Vault. Then perform a get from VSS, take those files and overwrite the ones you have on your disk. Then check in those files to Vault.
Reimport VSS database
Moderator: SourceGear