As a Team Manager, or a user with the "Manage list of users/roles" permission, perform the following steps to invite new team members.
Click "Team" in the top blue menu bar
Click "Members" in the grey bar (default selected)
Click "Add Team Member"
Enter the team members first name, last name, and email address
Choose which permissions to grant the new team member
Read Understanding Case and Team Level Permissions to learn more about the permissions options.