To add an extension to CCleaner Browser:
If you can add an extension to Chrome Browser using Windows 10 you should be able to use this method to install the extension to CCleaner Browser.
Find a web page that is advertising the extension that you want to add and has a place to click to add the extension to Chrome.
https://chrome.google.com/webstore/category/extensions may work to find the extension you want to use.
Then paste the web address of that page into the CCleaner Browser and hit enter.
Finally, click on "Add the extension to Chrome" and CCleaner will show a pop up telling you that you can continue and add the extension only if you accept the risks.
Accept the risks and the extension has been added.
