Google Chrome - How to install third-party extensions?

Issue

Upon trying to install extension for Google Chrome (out of the Chrome Web Store), the following error is displayed:

Download the extension to your PC (do not try to install it):
Right-click on the Install button and select "Save link as"
In the window that opens, choose the folder where the extension (.crx) will be saved and click on the "Save".
Under Google Chrome, click on "Customized and Control Google Chrome" > "Tools" > "Extensions".
Finally, drag the .crx file to the extensions page, to install it.