Ho to install an already downloaded .crx file extension in chrome?

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http://askubuntu.com – It download the .crx file from novell-moonlight- and then went to chrome://extensions/ and drag and drop the file on the chrome windows opened in that address and the following message appear Apps, extensions, and users scripts cannot be added from this website with an "OK" button and nothing more. I read something about "ExtensionInstallSources", but not know how configure it to install extensions from a local directory. Any idea? I'm on Ubuntu 12.04 64bit (HowTos)