You are referring to the third option Google would accept when there are multiple versions of a website. It wants us to use a "link canonical tag" in the <head> of the home page of the mobile version, pointing to the desktop version. See here for easy-to-understand information about this tag: http://www.mattcutts.com/blog/canonical-link-tag/
(It's not about just making a link on the page for someone to click on.)
The site you refer to gives an example of linking to the mobile site with a "link alternate tag." (Again, this is not a link a user clicks on.)
The purpose of the page was to tell you how you can help Google to search your pages efficiently, so this is good information to know if you have two web sites, one for desktop, and one for mobile.