To manage your team settings, you must be an team admin. As an admin, you will see the settings tab in your navigation bar; click Manage on the team you would like to access.
An admin has the option to add team members, add billing options, etc.
Team members will be able to send rewards using any available billing method, but will not have access to changing account settings.
For instructions on how to add a new team member/admin, click here.