The basic steps would be something like:
- setup a server
- select a web server software (IIS or Apache)
- install any and all prerequisites for the webserver software selected above
- install and setup a webserver (IIS or Apache)
- install any and all prerequisites for osTicket(PHP, Mysql/MariaDB, etc)
- create a site in your webserver config and test the site to ensure that it is functioning (including PHP)
- create a database in your database software
- create an empty database for the site.
- create a user in the database for the site, and grant that user permissions to the database created above.
- download osTicket from osticket.com.
- unarchive the download and put the files from the /upload folder into your site root (or selected sub folder off that root)
- Using your preferred web browser, browse to the site
- follow the steps on the screen to setup and configure osTicket
There are many guides I've seen floating around the internet so chances are you will be able to search and find one that is suited to the environment that you want to run.