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

This is a known issue.

Download the .crx file. Drag and drop the downloaded novell-moonlight-3.99.0.3-i586.crx file into Google chrome browser.

If you get any error mentioning "Apps extensions and user scripts cannot be added from this website", open chrome://chrome/extensions/ in a new tab and now repeat the step 1