This will show you how to export your RSS feeds from Outlook 2013 to any other program/service by OPML file.
Click FILE tab
Click Open & Export option
Click Import/Export button
If you get similar error:
You do not have permission to save to this location. Choose another location to save this file.
You are probably trying to save file in root folder like c:\file.opml. Choose any other folder to export the file, like c:\temp\file.opml