Show Calendar Events from Multiple Calendars in a Single View Using Calendars Overlay

We use the Calendars Overlay feature, available via the Ribbon, to roll up multiple calendars into a single presentation.

In my example,
I have three sites: Site_1, Site_2, and Site_3. I have a Calendar list on each site, and their names are Calendar_Site_1, Calendar_Site_2, and Calendar_Site_3.
But how do I show events from Calendar_Site_2 and Calendar_Site_3 on Calendar_Site_1.

Step 1. Open Calendar_Site_1 and click on the Calendars Overlay feature:

Step 2. Click New Calendar to add Calendar(s) from other sites:

Step 3. Enter Calendar Name, and select the type of calendar (SharePoint in the case of my example). Enter the URL of the website you just created and then select the new Calendar list and the default Calendar view. (Note that linking to Exchange calendars is the other option in the Calendars Overlay function.):

Step 4. Click OK

You can see that Calendar_Site_2 has been created in Additional Calendars:

Step 5. Repeat step 2 to create Calendar_Site_3:

Step 6. Click OK.

You can now see all three Calendar Lists shown in the same view: