The video tutorial explains the process to use a shared calendar in your Google account. You'll need access to a PC or Mac with a browser, and you'll need to log into your Google account as you would to access gmail.
Basically, you'll go to the calendar application and open it in a new browser tab, then add a calendar from a URL. Once you've added the shared calendar, it will be available on every device (including your mobile phone, tablet, etc) that has access to your Google calendar.
If you have an Android phone, you'll need to follow these steps once to have the new calendar automatically synchronized on your phone: https://youtube.com/shorts/pmWlvaPCZH8?feature=share