Chrome Web Store is the place we search and download new extensions for Chrome browser. Other than that, users can also find and get third-party extensions from the internet, such as those developers’ websites. You needed only to enable Developer mode in Chrome browser before installing a Chrome extension file in .CRX format. Here’s how to install a third-party extension not published on the Chrome Web Store. Note that you should ONLY install extensions from legitimate websites you trust.
Install Chrome browser extensions manually
Copy chrome://extensions/, paste it to Google search box or the Chrome browser address bar and press Enter key to open the Extensions page in Chrome web browser on your PC.
Click the Developer mode toggle to enable it at the top right corner on the Extensions page.
Locate the Chrome extension file in .CRX format in the file explorer on your computer. Drag and drop it to the Extensions page in Chrome browser. You will be prompted to confirm the operation. Click Add extension button to install the Chrome extension.