The following information will guide you on how to properly setup a sync or backup with your Windows Mail data:
1) Start by opening GoodSync.
2) Click Browse on the left side in GoodSync and select the following Windows Mail data folder:
C:\Users\<UserName>\AppData\Local\Microsoft\Windows Mail\
3) Click Browse on the right side and select the destination folder to back up to.
*Note: by default you are performing a sync, if you want to back up instead, first select Job > Options > 1- Way Left to Right, and then continue with step 3)
4) Start the sync/backup process by clicking the Analyze button.
5) Click the Sync button to complete your sync/backup.