'sudo apt-get install skype' in a terminal

through synaptic

or through the add/remove tab on the applications menu

once you have the medibuntu repositories enabled

https://help.ubuntu.com/community/Medibuntu

download this and install http://www.skype.com/go/getskype-linux-ubuntu , it
should work for 9.04 as well

See:
beginlinux.wordpress.com/.../

Just download the Linux version...............