The Default Team Members functionality enables you to specify team members for all accounts a given account owner (user) owns.
Pick the Default Teams tab.
Use the lookup button to select a user that owns account records.
Use the lookup button to add team members in the Default Team Members section.
Select the team role for each user. You can add, change, or remove the Team Role picklist values in the Team Members object. To set up team member roles:
In Setup, enter Objects in the Quick Find. Select Object Manager (or Objects in Salesforce Classic).
Decide whether to apply the team you’ve configured to all accounts owned by the selected user by checking the On Save, Automatically Assigned Default Team Members checkbox.
Click Save.
Now, when a new account owned by this user is created, their default team populates with these team members and team roles. Assign steps within your definitions to team members by choosing “Role” as the assignee type.