To add a user to a team project, please follow the steps below:
1. Log into the portal and click the 'Project Groups' menu item.
2. Select the project from the drop-down menu.
3. There are 3 pre-defined groups that you can add a user to. Please choose the group and click the 'View/Edit Members' icon. (You can refer to the Team Foundation Server Default Groups, Permissions, and Roles article that's available on MSDN.)
4. Check the desired members and then click on the "Save" button to add the user.