1. Navigate to Manage > Material Database.
  2. Open the MDB you'd like to edit by clicking the dropdown menu beside the Add button indicated by the arrow.  Click the icon for Share MDB next to the MDB title.
  3. Any users that the MDB is shared with are displayed in the box on the right. Click the X next to the names of users to unshare the MDB with them.
  4. Confirm the changes by clicking Save.