Download a good graphic program and touch with pen.
Operation System is normally Android.
it must have more than only one program for it, but they would not be freeware.
I'm afraid if you're looking to draw on a tablet device, you're not going to find much aside from glorified finger-painting applications. Wacom or any other company has yet to release a consumer electronics pressure-sensitive stylus based tablet computer to do serious digital painting on.
The market is most likely seen as too niche, it would basically be a portable, computer-independent, battery powered Cintiq.