The settings on creating and assigning equipment to rooms are found in the equipment settings page, so before you can create a room you need to have a piece of equipment in your lab ready to assign to it.
Edit the equipment details and select 'Show optional details'. Here you will find a drop down menu for the Room.
You can select to assign the equipment from any existing rooms in this list, or to create a new room, simply type the name of the room in the box. You will see a 'Create' button appear after you have typed the name. Click this, and the new room will be selected for you.
The next time you go to assign another piece of equipment to a room, the newly created room will be in the list of rooms for you to choose from.