To register a new resource, click on the yellow  icon and fill in the form, describing the new resource and to which building it belongs. It's strongly advised to fill this in as much as possible, and to keep it updated so that users can use this information when choosing a location for an event.

In Room settings you can Allow calendar-based room release, which will automatically release booked rooms that are no longer needed because it was cancelled or the attendants declined the invitation:

Click ADD RESOURCE to save the new resource.