Insert the Ubuntu install CD / DVD / USB stick into your system and boot from it. When you install the OS in a virtual machine like I will do it here, then you should be able to select the downloaded ISO file as a source for the CD/DVD drive in VMWare and Virtualbox without burning it on CD first. Start the server or virtual machine, it will boot the system and start the installer.
1 – Login on vCenter/vSphere
