Depends on where you want to put it, but I don't think there's anything built in that deals with AdSense. If there is, I haven't found it.

You've always been able to drop an adsense codeblock into the appropriate spot in a theme.
Some people use plugins to do clever things like put it after the second paragraph of a post, or put it after the third entry on an archive page.
But general use? Drop the code in the HTML of a them page, just like you would on any other type of site.

Or you can put it in a text widget. Or you can do like I do on some sites, and use a nifty little plugin called samsarin that lets you put PHP code in a text widget - then you can write something up that alternates ads.