Manually Assign a Territory to an Opportunity
On an opportunity record, your organization can keep track of the territory whose
assigned sales reps work that opportunity. The territories available for assignment are determined
by the territories assigned to the account record that the opportunity is associated with. When
you assign a territory to an opportunity, that opportunity is shared with all Salesforce users
assigned to that territory's parent in the territory model's hierarchy.
So you can make assignments and users can view them, make sure that you add the Territory field to your Opportunity page layouts. Then let your users know that this feature is available.
When you archive a territory model or delete a territory on an active model, the Territory field is reset to a blank value on opportunity records with those territories assigned.
Example
If account Unitel.com has six opportunities and two associated
territories (East Coast and West Coast), you can assign either East Coast or West Coast as the
territory for any or all of those six opportunities.