On the Team Management screen, you can invite your team member in the following steps:
Step 1: Enter member's email address
Click here to understand different user roles.
Step 2: Select the environment you wish to give access to and in the drop-down select the role you wish to assign to the team member. Click here to learn more about Live/Test environment.
You also have the option to give access to only one environment (Test or Live). Just un-check the checkbox for that environment.
Step 3: Click on "Send Invite" button and an invite email will be sent to the member to join your account. Refresh the page to see the user in Current Team Members.