Google Adsense for feeds can be added to your Feedburner feeds easily via your Google Adsense. Presently the Feedburner suggests "To activate AdSense for feeds, sign in to AdSense and then look for the AdSense for feeds link ..." under its Monetize tab.
For adding Adsense you need to have an approved Google Adsense account and you must be an approved publisher. We will try to add the Adsense for feeds below each post of Feedburner.
# 1) Login to your Google Adsense (You need approved Adsense account)
# 2) Click on "My ads" (top-left) >> Feeds (left tabs)
# 3) Click on "New feed unit". It will open "Create new feed unit" page.
You can select the options as per your needs. I am attaching my own selection.
Chances are that Adsense might have already created a channel, if not you can "Create new custom channel". Channels can be considered as names to track the performance of the ad units.
# 4) Chances are that if you have burned the feed with feedburner using your same adsense user ID then the "Save" button will be active. If it is not active it means that Adsense cannot find any orphan Feedburner feed and you will have to "Burn new feed". The steps should be same as told in How to use Feedburner
Hopefully this should get your adsense for feeds activated and you should find the adsense ads below or top of feed items as you opted during creating of new adsense feed unit.
# While Google feedburner service can be used instantly, using adsense for feeds requires an approved Google Adsense account for showing the ads.
# Adsense for feeds are CPM (cost-per-1000) Impression ads. So if you have full text feeds, users are more satisfied and will keep coming back to your feeds resulting in better Adsense impression for your feeds.
# Adsense for feeds does not allow you to choose the ad unit size. The ads units size with the feedburner feed will be either 300X250 or 468X60 format only. However you can select the ad types and colours of Adsense ad units.
# Google Adsense does not declare the revenue share for the ads. However your adsense earnings will always report the earnings from your feed.
# While Adsense have maximum limitation of 3 ads and 3 links, Adsense for feeds do not have such restriction. The number of ads are determined by Adsense and in their words :
"... variable ways in which feed items are displayed are controlled and optimized automatically by the AdSense for feeds application and the choices you make as a publisher in your AdSense account when configuring your AdSense for feeds ad units. This means we may automatically suppress ad impressions when we detect there are too many feed ad units being displayed, resize ads based on the size and length of your content, and adjust the ads that are displayed based on the device in which the feed is being read.".