Hi Jake
If you want to do this on the phone, you'll need a file manager to access the sdcard. Astro is a very good one.
If you want to it on the computer, you need too hook the phone to the computer via the usb cable. Once it loads the sdcard slide your notification tray on the phone and mount the card to the system. Then you'll be able to access the card on the computer. Make sure to unmount the card by slideing the notification bar down and selecting unmount when you are all done before you take it off the cable.