Convert Calendar on website to an exportable calendar

Hello. I go in a school that uses a system called [login to view URL] and i want that calendar exported to my google calendar. The problems with this can be that there sometimes are attached files to the lessons, and before you are able to see these files you need to be logged in. I got a storage to host the files from the lessons if that is needed. I need it to be on a website so not only i can use it but everyone else can use it too.