That's not much to do with osTickets mate, you have to configure your webserver to use SSL to secure the connection. If you have that setup already, try setting the Helpdesk URL to https://your.domain/ then use a redirection for non-ssl connections in your webserver config.eg: https://stackoverflow.com/questions/4083221/how-to-redirect-all-http-requests-to-httpsAgain, depends on what server you are using.