V3 has a feature that shows you the dismounted databases in your BCM
database folder, and lets you select one of them. This should work
whenever you go to menu BCM|Database Tools|Create or Select a Database.
You don't have to uninstall and reinstall BCM.
In earlier versions, you need to mount the database yourself, using
osql (already installed on every system) or sql tools.
Note, that mounting (or attaching) a database to the sql server engine
is different from importing a file.