Did you just copy the iso file to DVD? The Iso needs to be burnt to disk and not just copied. If you prefer to use a DVD download Imgburn and use the option 'write image to disk'.
Personally I always extract the iso to a usb stick and install from there. You need to prepare the USB stick first. Some easy instructions on this link.
As you have an iso file, I wouldn't do step 5 and onwards. Instead, once you've exited diskpart. Just right click on your iso file and extract to the usb stick.
Don't forget to change your boot options in the bios to boot from usb.