First option: Site Overlay. Site Overlay doesn't require any downloads or configuration. To get to site overlay screen please go to All Reports -> Content Optimization -> Navigational Analysis -> Site Overlay. Besides number of clicks you can see the quality of the link.
Second option: Edit your html code. If you want to count some links (like number of clicks to some external websites) you must add:
onClick="javascript:urchinTracker('/My-Links/Example');"to the <a> tag. Like this:
<a href="http://www.MyWebsiteAdviser.com" onClick="javascript:urchinTracker('/My-Links/MyWebsiteAdviser');">Visit www.MyWebsiteAdviser.com!</a>
One more thing, Google tracking code must be placed in your HTML code above any of these calls.
Enjoy,
Alex Webs