I found this article to be a great help when I started out on doubles:
DDR Freak - How to play doubles
The more you play it the more you pick up on how streams all work together. Once you can read the streams, hitting everything isn't too hard to do. The part that I found hard was getting my legs to cross right for those moves across the pads.
I'd check out some people who are fairly proficient at doubles and watch how they turn their body and move their feet. You'll get a good idea of what's going on soon enough.
As far as your pads go... pads shouldn't be separated. That is, you should find a way to fix them right next to eachother. There's some brief stuff in that article above about it, too.