Share your screen using Back to My Mac
If you use iCloud and have several computers connected to the Internet, you can use Back to My Mac to share the screen of one computer with another computer.
For example, if you have a Mac at home that’s connected to the Internet, you can share its screen with a Mac you use at work. You can control that Mac, move files and folders, open or close apps, and even restart it.
Set up Back to my Mac
Follow these steps for each computer whose screen you want to share.
Choose Apple menu > System Preferences, then click Sharing.
Select Screen Sharing or Remote Management.
Next to “Allow access for,” select “All users” or “Only these users.” If you permit only listed users to have access to the screen, click the Add button
and the Remove button 
to edit the list.Choose View > iCloud to open iCloud preferences.
If you aren’t already signed in to iCloud, enter the Apple ID you use with iCloud, then click Sign In.
In the list of iCloud features that appears on the right after you’re signed in, select Back to My Mac.
To stop sharing your screen using Back to My Mac, open iCloud preferences, then deselect Back to My Mac.
Connect to your remote Mac
To see your remote computers in the Finder sidebar, choose Finder > Preferences, click Sidebar, then select Back To My Mac in the Shared section.
Open a Finder window. If no shared computers appear in the Shared section of the sidebar, put the pointer on the word Shared and click Show.
Click the remote Mac, then click Share Screen.
If you don’t see the Mac you want, click All to see all the available computers, select the one whose screen you want to share, then click Share Screen. All computers that are signed in to iCloud using the same Apple ID as your computer and use Back to My Mac are shown at the top of the list.
Back to My Mac requires a router that supports NAT Port Mapping Protocol (NAT-PMP) or Universal Plug and Play (UPnP) to share services. Check the documentation that came with your router to make sure it supports NAT-PMP or UPnP.