Log in to your admin account and go to Exchange admin center
Go to the Recipients → Resources section.
Click on + to create a room.
The name and e-mail address are mandatory fields. The mailbox cannot be changed later on.
Creating Room Lists (Room Lists Distribution Group)
Rooms created in the previous step should be included in a room list. This allows correct behaviour in different Outlook or Outlook Web Access versions. To create a room list, you need to use PowerShell Console. For a guide to logging in to PowerShell see below.