To invite one or several persons to register a user account in YouTrack:
- Go Settings → Users
- Click the New User... button and then select the Invite Users tab.
- Provide a list of space-separated email addresses which owners should be invited to register an account in YouTrack
- Click the Invite button to send invitations to users with the specified emails.
Please note, that email notifications should be configured and functional for this to work.