1. Open Google Calendar, and click on the Create button.
2. Before filling out the event, click on More Options.
3. Click on the Rooms option near the guest list.
4. Select the Room you would like to create an event for.
If you see a room that is crossed out, then the Room is not available for use. This also applies to not having the necessary access to create an event in that room. Certain calendars may require approved access before an event can be created on that calendar.