Just log into your Blogger account and head to your Settings page where you can enter your Feedburner feed address and save it. Done.
The beauty of doing this is that now you get a fuller picture of your Feed stats. Those subscribing to your old blogger feed will now be counted in the overall Feedburner count and you’ll now be able to track what they do with your feed like you can with those who were subscribing via the Feedburner feed previously.
Your feed counter might even go up a little (although in reality the number of subscribers to your blog isn’t really changing – it’s just counting everyone now).