You can view users under the Users tab of Organization Settings. To add invite new users, click Invite New User on the right side of the page above the user list search bar. Then fill
Fill out user details and click then click Save. This will send the new user an invite via email. Remind new users to check their spam folder if they can't find the invite!
User permissions
To give an invited user permission (or edit permissions for an existing user) click + Add a Team to add a new team, or edit the "Manager" and "Can Write" permissions for an existing team.
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