See http://code.google.com/p/feedformatter/w/list for instructions.
Feedformatter requires some version of ElementTree.
There are two versions of ElementTree - the Python version and the C version. T he C version is faster, but feedformatter will happily work with either version. It chooses the fastes version available on your system.
Modern versions of Python have ElementTree in the standard library so feedformat ter should "just work".
If you have an older version of Python, you'll need to make sure ElementTree is installed in your site-libs directory. It's in PyPI so you can just use easy_in stall.