How to ember the osticket form on my website HTML page?
You can either use iFrames, or make your own simple ticket open form and use it with the Ticket API.
See Admin panel -> Settings -> System: at Allow System iFrame: https://docs.osticket.com/en/latest/Admin/Settings/System.html?highlight=iframe#
Or for API https://docs.osticket.com/en/latest/Developer%20Documentation/API%20Docs.html https://docs.osticket.com/en/latest/Developer%20Documentation/API/Tickets.html