If you have installed OSTicket to your webserver then people can access the site and open tickets by going to it with their web browser.
If your site is domain.ext, and your installation is in /support they would go to:
www.domain.ext/support(www.domain.ext/support)
And you/staff would go to
www.domain.ext/support/scp(www.domain.ext/support/scp)
to access the admin panel.
Directions on how to setup cron are located in the wiki:
http://osticket.com/wiki/POP3/IMAP_Settings(http://osticket.com/wiki/POP3/IMAP_Settings)
Obv. if your running under Windows you would utilize Task Scheduler instead.