Installing Google Chrome extension [CRX Format] is just a single click process if you have already configured Google Chrome for extensions. Previously we shared article about how to install PageRank extension in Google Chrome, this time we would like to share how you can install Gmail extension in Google Chrome. After download.crx file. Run Chrome; Chrome menu -> Tools -> Extension Manager; Drag the.crx from windows explorer, and drop it in the Chrome extension manager, then will start install.