Hello Steve,
Assuming that you were able to burn the Windows 7 ISO file to a DVD, that is your "Boot Media". What may be happening is that your first boot device - the device your computer boots from - is not your DVD drive.
To get around this, reboot your computer and as you do press and hold the F12 key. That will bring up a menu that will allow you to select the DVD burner (player) as your first boot device. Select that, insert your DVD, and press any key to start the installation process.
Let me know if this helps you out.
Regards,
BearPup