Unfortunately there is no .deb installation for Skype under XUbuntu that I know of. The best I found is to install the support of 32Bit environment and then install the standard 32 Bit skype as follows:
Based on ref: http://askubuntu.com/questions/343047/installing-skype-on-ubuntu-13-04-64-bit
sudo dpkg --add-architecture i386
sudo add-apt-repository "deb http://archive.canonical.com/ $(lsb_release -sc) partner"
sudo apt-get update
sudo apt-get install skype