You create desktop assignments in the Administration Console to provision virtual desktops to your end users.
Your Horizon Cloud environment must have at least one image VM in the Published state that the system will use as the operating system on the virtual desktops. In desktop assignments, the published image is used as the Microsoft Windows operating system in the desktops that get assigned to your end users by the desktop assignment.
For nodes in a Microsoft Azure environment, before creating a desktop assignment, you must have at least one desktops farm that was created based on the published image. See Create a Farm.