There are a couple of BRMS commands you can use to add media to a media pool:
Add Media to BRM – Help
The Add Media to BRM (ADDMEDBRM) command adds a media volume to the BRMS media inventory. The volume can be a volume from another media inventory that contains active data, the volume can be a volume from some other outside source, or a new volume that you want to initialize. Once added, BRMS tracks the volume’s characteristics, location, use and content.
When you add the volume, you must specify the media class of the volume. You can also specify how you want the volume to move, where the volume is located, its container (if any) and other miscellaneous attributes.