It doesn't matter if you are planning a mass deployment or just want to install the Chromebook Extension on a single device. Either way you need to start with the manual installation process.

Manual Installation

Step 1: Manual Chromebook Installation

Step 2: Assigning your Devices by pass this step by creating an Automatic Assignment Key

Step 3: Finished -  Please see Getting started with the web console

Continue if using the Google Chrome Management Console to push out the extension

Step 4: Export Configuration File

Step 5: Install extension with Chrome Management Console

Step 6: Upload Configuration file with Chrome Management Console

Mass Deployment Process Finished:  Please see Getting started with the web console