You can choose how often ads appear in your feeds - with every post or less frequently. Ads can appear at the top or bottom of posts, and you can change the color scheme.
You can also choose the length of posts that receive feeds. This is particularly useful if you tend to have the occasional one or two line quick update. You can save your readers annoyance by skipping the ads in those posts.
At the bottom of the screen you can see a list of feeds available. If you are new to AdSense for Feeds, there will be no feeds listed here.
If your feed is not listed, and you're not using FeedBurner Ad Network, click on the burn a new feed link at the bottom of the screen.
If you were using FeedBurner Ad Network, your feeds may not have been migrated to AdSense for Feeds. As of this writing, manual account migration has been disabled, so you'll have to wait until that's reinstated or all accounts are automatically migrated.
