Log in to your account and go to "Locations" under "My Page". Click on "Add a location" at the top right corner and you'll see a form. To add a new location, fill in the Name input field. You can optionally add other information related to that location.
Once that's done, scroll down and click "Save" .
Alternatively, you can also auto-populate the form from the Ofsted URN of that location. On the "Locations" page, click on "Add a location" at the top right corner and click on "Prefill from Ofsted register", again at the top right corner of the page. Insert the URN and press enter to select the matching location. Once you've selected the location, the form should be filled in automatically based on Ofsted records. If you're happy with it, click "Save".