Hi John,
Are you trying to upload this file to method? Or have the file generated based on data within Method?
If the latter, A Report would certainly be the simpler of the two options, as there isnt a quick way to export/generate an XML file with any existing actions. That being said, members of our consulting team have built solutions around generating XML files, but the process (including testing etc) can be quite lengthy, and I would suggest if you have a choice of either, the Report route is certainly the simpler of the two options.
Also, if you were curious what an XML file was... http://whatis.techtarget.com/fileformat/XML-eXtensible-markup-language
Thanks John.
-Ben