To add or remove a user from a team, you will first of all need to navigate to the "team" page using the menu in the top left and selecting "teams".
Expand the root team using the ">" button to display all of the teams available for you to edit.
Select the team you wish to edit the users for and click the "Edit" button next to it.
Once in the teams edit page, scroll down to "Users".
To add a member, begin searching for the person or use the "show all" button and find the user in the drop down list. Once you have found the member you wish to add, click "add" next to their record.
This will then add them to the team.
To remove a user, find the user in the list of users already part of the team and then click remove.
When prompted, click "delete" to remove the user.