After you created a list of territories, you can add territory to any of your clients.
Open page Addresses.
You will see a list of all your clients. You can also switch to list of sites.
Open the client you need. Page with his settings will be opened.
Click on Territory field. List of all available territories will be opened in dropdown menu. Choose the one you need.
After you're done, click on Save and close button to accept changes you made.
This way you can set territory to all your clients and sites.