The Team tab is available on the Agency plan. From Settings > Team, the account owner can invite collaborators to access it: enter their email address and click "Invite".
For each member, you set their permissions per connected site: Read (view only, no AI action is sent for this site) or Write (the AI can propose actions on this site, which the member can then approve or reject). These permissions are independent from one site to another.
To remove a member's access, click "Revoke" on their entry: this cuts off their access to your account, without deleting the actions they've already approved.