The problem with YDL
There are no codecs installed due to licensing issues with the free distribution of Linux. This means that you have to install them yourself.
Having installed and configured a few Linux boxes before, I knew codecs are freely available through 3rd party repositories (read: 3rd party software), but I was surprised to learn that because YDL is a Fedora/Red-Hat build and is specifically PowerPC architecture, these freely available codecs I had bookmarked were no good.
Do not despair! Codecs are available. You just have to pay for them.... yes . pay... as in, money.
http://www.fluendo.com is where you need to go for them, where most codecs cost between 7 and 16 Euros. They cover the most popular ones fortunately, and MP3 itself is a free download if you register.
All the instructions to install are contained within the zip file. However, to copy a file into the operating system directory you will need to log out and log back in as username "root", with the appropriate root password.
This is as far as I will be taking you in the how-to, but 5 minutes on Google should provide you with enough to do in YDL.