The easiest way would be to use a chrome extension or a Firefox extension using your favorite browser for SEO. These extensions frame links of a web page with nofollow in red.
Chrome Nofollow extension:
https://chrome.google.com/webstore/detail/nofollow/dfogidghaigoomjdeacndafapdijmiid?hl=en
Firefox nofollow extension:
https://addons.mozilla.org/en-US/firefox/addon/nofollow-advanced/
Safari and Opera nofollow extension:
www.igorware.com/extensions/nofollow
example:
