I have moved this into a new thread---please do not "hijack" existing threads with only loosely-related questions.
The typical option is "burn from iso" or maybe "burn from image". If you tell us the choices you are looking at, then we can pick the right one.
You say that you have a blank DVD, but you imply that you have a CD image ("Simplymepis-cd"). If it's a CD image, then you you need a blank CD.
Also, why Mepis 6.5? The latest is Mepis 8 (Very good distro---my default at the moment.)