After having installed the Appspace extension in Chrome of a Chromebox, you have to register the Chromebox in Appspace.
This document explains how to do it.
This procedure can be also used later to register again a Chromebox (to fix an issue,...)
You should see this screen with the register code:
Note the code and send it to administrator of Appspace application.
Go to the Appspace Network site where you want to put the Chromebox:
Go to the devices menu and click on the ADD button:
Enter the register code, the Chromebox name, and select the channel:
Just after this operation, the Chromebox will start to display the content of the channel selected.