A team member's email address/ log-in password can only be changed by that team member, not by any other team member or the primary account owner. Primary account owners can add and delete team members.
To update your email address, go to Settings>>Team Members and select Change your email/password.
You will be redirected to this page:
Enter your new email address, update your password if you need to and select Update.
Your new email address and password will be saved.