Download the Chrome Extension from the Google Web Store:
https://chrome.google.com/webstore/detail/thanksio/pmghhbcidenacjapeocgagkkaffnbfdd
Once added, you'll see the icon to access the extension at the top right corner of Chrome.
For instructions on how to use the extension, click here: http://help.thanks.io/en/articles/3767508-how-to-use-the-thanks-io-chrome-extension