If I'm not mistaken, you should be seeing a list of locations, with two entries at the top which are one dot, and two dots. Scroll to the two dots, and press the Enter key, and do this a couple more times until you see a folder named "media" in the list. Scroll to this, press Enter, and look for an entry that's something like "mmcblk0p1" (it may be something like "mmcb2k0p1", depending on what slot your SD Card is in). Press Enter on this entry, and you should now be browsing your SD Card and should be able to find your disk or tape images.
I hope that makes sense - I don't have my Pandora open right now. If it's not clear enough, I'll rewrite it later.