In this pop-up, click the Sogou browser icon, then click [Download Offline Package] to save the extension ZIP file to your computer. Or, click here  download offline package directly.

In the browser's top-right corner, click "" icon [Application Center] [Manage Extensions]

Turn on [Developer Mode]

Once Developer mode is enabled, drag and drop the downloaded ZIP file (do not extract it) directly into the page. After installation, you can delete the original ZIP file; it will not affect the extension.

After installation, click the "Pin" icon to keep the extension icon in the browser's top-right corner.

Note: You can ignore any errors or "Service Worker (invalid)" messages after installation. The extension will work normally.