To link to your OSTicket installation just add a link to the URL as follows:
http://www.yourdomain.com/yourOsTicketInstallation(http://www.yourdomain.com/yourOsTicketInstallation)
Replace yourdomain with the domain you installed on and the path or installation directory you installed OSTicket in would replace 'yourOsTicketInstallation'
Something like, http://www.mydomain.com/helpdesk(http://www.mydomain.com/helpdesk)
Hope that helps!
Steve