[ubuntu] Installing on old iMac

Hello all,

I have an old iMac, 2006 Core 2 Due 1.83Ghz, that has a new hdd in it, so there is no installation of OSX at all. It had an installation of Linux Mint on it, but I want to change it to the newest Ubuntu (Mate, in this case).

Here is where I am stuck. I try to boot off of the CD, and I get to the screen that has 1. 2. Select CD-ROM Boot Type: and nothing more can be done as the keyboard has not been activated.

Does anyone know what I need to do to get the CD to boot?

Thanks,
RMFlagg