Chrome Remote Desktop
Add the Chrome Remote Desktop app to Chrome via the Chrome Webshop.
Click on this button and start Remote Desktop
Click on the green button Share to install Chrome Remote Desktop Host.
The user, whose computer you wish to take over or share, must click on Access next to See and control a shared computer.
Enter the 12 digit access code you get from the user.
In order to share the computer over a longer period both individuals must be logged into Chrome. You only need to do this once.
Then click Access Remote Connections and enter a pin code of your choosing. The user who needs to remote control your computer needs this pin code.
Sharing over longer period also works after a reboot of your computer. The user, whose computer you controls, can even close Chrome Remote Desktop without loosing the connection.
Click Stop sharing when you are done.
It is not necessary for Chrome to be running in order to use Chrome Remote Desktop. All you need to do is be logged into Chrome, not Google, and click on the button Activate connections. After that you can close Chrome webbrowser.
More help can be found here: https://support.google.com/chrome/answer/1649523?hl=en