rel="nofollow" is a parameter than can be added to a hyperlink so that your "link juice" doesn't flow to that page.. The way to do this from within a Content block is add the hyperlink then access the link advanced tab, There is a drop down box titled something like "relationship to this page" towards the bottom you can select nofollow.

If you want to simply exclude search engines from particular pages on your website, it would probably be easiest to add them to the robots.txt file in the root.