Sync events between your subsites and main websites. Changes in the main one will be inherited by the subsites. you can set these up in the admin panel.
How to work with MEC multisite Event Sync Addon?
You can now sync events in your subsites with the main website and any changes to the main website is inherited by the subsites. You can select the subsites to be synced in admin panel.
When you hit Save Changes in Modern Event Calendar Multisite Event Sync Addon, a new section will open and there you can configure the event.
Select which events you want to sync with your selected websites and click Sync Now.
Every event on the site you have selected will be synced and then you will see the Sync Successful message.
Source : https://nulledfree.net/o1dm0c