Go to Organisation Settings > Users and Roles
Select an existing contact or add a new contact.
For an existing Contact: Enter their email address and TidyHQ will send them an invitation email with a link to login.
For a new Contact: You can enter the email of a person who is not yet in your TidyHQ as a Contact - they will receive an invitation to create a profile and login.
Select the TidyHQ User Rights relevant to position/role within the organisation.