Log in to Salesforce as Administrator, and create users in Salesforce for the Team Leads. Then create Teams and assign them to the team leads.
Click here to know more about creating users
Once you have created the users, go to the teams tab and click the new button, enter the Team Name, Description, and select the Team Lead from the user's list and click the save button. Now the Team is created and the team lead is assigned to the team.
Note: If you have already created the Users, you can assign Teams to the Team leads(users) at the time of creating Teams. If you have not created the Time Tracker Users earlier, then create Teams and then assign Teams to the Team leads from the edit page of Teams.