[Proto]

I've installed yum and followed instruction on that pages. This what i got when i type
yum install kdemultimedia-extras on console:

You might only want to download the package you want instead of the whole suite for kde (which will be vastly useless since you are most probably running gnome ) with

yum update
yum install xmms-mp3 (or whatever the filename is)

Another thing you might want to try is getting the rpm, just google for
rpm, mp3 and xmms. Download the corresponding rpm and install it from console with

rpm -i xmms-mp3xxx-xxx.rpm

change the filename for the corresponding one