Compliance Kit - User Synchronization with Existing Object

When using the Compliance Kit, how can I point the User Synchronization module towards an existing object ("Employee") which has a single-select property for login account ("Login Account")? Each "Employee" record has properties that are populated through M-Files Importer, and then we populate the "Login Account" property manually. We would like to use Compliance Kit to fill in the property automatically, based on the "AD Login" property (formatted as "domain/username") that we pull in from the importer. It seemed like User Synchronization was the right path.