In Google Calendar, on the left side, locate 'Other calendars'. Click the + sign > Browse Resources. Select High School, and select High School-1-HS Flex Office (15).

If you do not want to constantly see appointments for this calendar, toggle OFF as needed.

On your Google Calendar, create a new event. Click 'rooms' where it says Add rooms and location. Select High School -1-HS Flex Office (15). Add remaining details and/or guests to the event and click Save.