Which roads to I take for the Blueridge Pkwy?

My family and I are moving from Portsmouth, VA to Austin, TX in about 2 weeks. We want to take the Blueridge Parkway scenic drive. I've been looking everywhere to try to find out where we would get on and whatnot. I can't find anything... Does anybody have any info. about this drive? Where I can get on from Portsmouth, Va? Is there an entrance in Roanoake? Or would we have to drive to Shenandoah? I really have no idea. Please help! Oh, and yes, I know that the Blueridge Pkwy, doesn't go all the way to TX. It's supposed to connect VA and TN, correct?