How do I install Ubuntu on a brand new laptop with only FreeDos on it?

How do I install Ubuntu on a brand new laptop with only FreeDos on it?

I just bought a Lenovo IdeaPad G500s (Intel® CoreTM i3, 4GB of RAM,
GeForce GT 720M) with only FreeDos on it. I decided to install Ubuntu
13.04 on it and followed the steps from this page:
https://help.ubuntu.com/community/Installation/FromUSBStickQuick After
choosing to boot from the the stick, a black and white menu appears asking
me to choose between trying Ubuntu without installing, installing, OEM
installing and checking disk for errors. However, no matter what option I
choose, I get the following message: error: invalid magic number. error:
you need to load the kernel first.
Press any key to continue...
After I press something I get back to the menu.
I must mention I am just an average user with very little knowledge about
computers and programming.