It will open classera class (teams, zoom or whatever link) automatically at the specified time of the class. optinally if you configure the sound using the link below, it will beep.
Download the zip file then install it manually
You need to explicty change the settings of the site to allow playing Audio (see https://www.tenforums.com/tutorials/116467-allow-block-sites-play-sound-google-chrome.html)