When creating or managing a team there are a few different privacy settings to choose from that determine how people can join that particular team.
To change a team's privacy settings as an Organization Admin
Sign in to your account
Navigate to the Admin Dashboard by clicking the ADMIN Tab at the top of your page
Find the Team you wish to update in the Team list on the left side
Click the "edit" button under the team name to open the Team Settings
The 3 different options available for an Organization Admin to choose from
This option will allow existing account members to find this Team in the Team Directory and request to join. The Team Admin will be notified and still need to approve this request before anyone is able to become a member of the team. Click here to learn more about the Team Directory.
When this option is selected members must be invited directly by a Team admin either via email invite or by sharing the team invite link. Private Teams will not show up in the Team Directory
Hidden teams allow Organization Admins to build a team view that is only visible to admins. Members added to this team will not be notified nor be able to view this team. Only existing organization members can be added to a Hidden Team. You cannot invite new users to a Hidden Team
If you do not see the Discoverable option you may need to enable the "Discoverable Teams" Feature for your organization. Click here to learn more about this configuration option.