To get started, click on the Publicize tab for the Feedburner feed you want to work on (if you haven't converted your RSS to a Feedburner feed yet, it's easy to do: just go to the Feedburner homepage and follow the instructions there).
Then, from the list of services on the left, click on BuzzBoost.
Then, choose your Settings and Content options (you can change any of these options later on). You can choose to display just the titles of the posts, or the contents, too.
When you are done, make sure you click on the Activate button at the bottom of the screen.
Here's an example of a Buzzboost feed showing the latest 10 posts at Latin Via Fables: