1. If you’re using Lightning Experience, switch to Salesforce Classic.
2. Open the account you want to assign territories to.
3. On the account’s detail page, in the Assigned Territories related list, clickAssign Territories to see a list of your organization’s territories. Adjust the list view if you need to.
4. Select the territory model that contains the territories you want to associate.
5. In the Available related list, select the checkbox for each territory you want to assign. If you need to view more records, click More beneath the list. Each selected territory appears in the Selected related list.
6. Click Assign.