First download, install and configure Hfs (PSPortal) with this how to: psp.servegame.com (You don´t need the "RSS, Live Music Streaming" Part)
Create a Folder for your RSS Files and share it like your MP3 Folder as a real-time folder with Hfs.
1) Edit Filename, Title and Description or choose the "Use Subfolders" method. Then the choosen Subfolder of the first level (NO subfolder in a subfolder!) of your shared MP3 Folder will be used as Filename, Title and Description. (optional)
2) Choose your, with Hfs shared, RSS and MP3 Folder and edit the HTTP Address - it musst point to your MP3 Folder. Save your Config - or reset it (optional) What the App is doing: if path.dat found, then reset to this save - otherwise reset to default).