I spent three hours on this the other day so I thought I would share a tutorial I found on how to link your Analytics and AdSense accounts. They've buried this one pretty deep in the settings!

Link your adsense and analytics

Note: You can only link to one 'account'. And, that's not one email account associated with your analytics. It's one official ANALYTICS account within your overall account. I know, really confusing. But beware because I don't think you can do this twice.