I am trying to build a virtual machine running Ubuntu 13.04 on a server running 12.04. I don't have any GUI. How can I download the iso file to 12.04 server using wget? I want to download the 13.04 server edition 64-bit.

wget http://releases.ubuntu.com/raring/ubuntu-13.04-server-amd64.iso

You may further refer the manpage for the wget command