After installation in your browser, it adds a similar pages icon in omnibar.
Now open any website in your browser. To find the similar pages or website, click on the icon added by this extension. It will open the similar pages with thumbnails.
It works by searching similar pages in Google. When you click on the icon, it sends the search query to Google and fetch the similar pages for you.
There are not much options in the tool. But this is a nice tool for finding similar pages without need to use any third-party tools. And you do not need to go to Google and search for few keywords to find a website.