To visit calendars shared by your friends you can:

When friends share their calendar(s) with you those calendars will not show up by default in your list of calendars. "Calendar Pinning" allows you to "pin" a friend's calendar to your list of calendars. You can think of this calendar pin like a bookmark or shortcut. Your friend's calendar is not in your account, but the calendar pin allows you to quickly access important calendars shared with you from your own list of calendars in the Navigator.

First you will need to go to the calendar that your friend has shared with you that you want to pin to your account. Follow the steps in the image below:

To pin a friend's calendar to your calendar list you will then need to follow the steps in the image below:

Now when you look at your list of calendars you can see both your calendar(s) and pinned calendar(s). When you are looking at your list of calendars you can see what calendars are yours (they have a calendar icon beside them) and what calendars have been pinned (they have a pin icon beside them).

Learn more about how to unpin calendars from your account.

Team Account Calendar Pins

If you are part of a Team Account then anything that is pinned in the master account for your Team will appear in your account's list of calendars. You can tell if a calendar has been pinned from the master account if you click on the pin icon next to the calendar in question and you will see the below message: