The answer to the question is, you actually don't. MediaShout does not care where you keep your media files, just so long as it can access them. MediaShout simply references the file path and displays it from there (preventing the need to place it in a certain folder or import it or creating multiple copies of the same file on your computer).
So you may ask, "Is there a good place to keep them?" Unless you have to keep things stored on a network or server, I will always recommend storing and organizing your media files in the "Media Shout" folder. This is located at Macintosh HD>Library>Application Support>Media Shout. This is not a magic folder where MediaShout will automatically find your files, but is a great place to keep the things you use (such as scripts, pictures and videos) in MediaShout. In this folder you are free to create new folders for the things you want to keep organized for MediaShout. Folders called Presentations, Pictures or Videos are just a few examples.
The reason I suggest this location is two fold:
(1)If a computer has multiple user accounts, since the Media Shout folder is in a "public" location on the system, all users will be able to access the files.
(2) If you need to transfer the software to another computer, simply copy over the Media Shout folder and put it in the same location. Then all of your files will be in the exact same physical location as they were on the old system and MediaShout should not have any issues locating the files applied to your Lyrics, Scripts or Templates.
So as you add new media to the computer, just make sure you place it where you want before you use it in MediaShout, and try not to move it after you have used it (or the links will break).