The current Monetize tab allows you to apply for an AdSense account (or link your Blogger blog to an existing AdSense account). You can then choose where to place ads on your blog, and once ads start appearing on your blog, review your earnings. We use the AdSense API to pull your live earnings data from your AdSense account, so now it's easy to check how your revenues are doing without leaving the Blogger interface.
Please note that new applications may take a few days to process, and not every site will be approved (for more on the eligibility criteria for an AdSense account, please see here). Details about the monetize tab and the information presented there is available in Blogger's Help section.