You can download C2 (to install on your system) by going to the C2 home page (click here), and selecting the download tab. Alternatively you can scroll down to the bottom of any page, where you'll find a download option, which provides links to the latest stable and beta releases.
And as RookieDev mentioned, don't forget to add your license doc to your documents folder.
Edit: once you put the license file in your documents folder, your copy of the software is automatically recognised as a full copy!
Hope that helps.