If you turn on your pen display and see a NO SIGNAL message, then this is a difference kind of problem. Instead go here: Troubleshoot the NO SIGNAL problem
Does you computer detect the display in the tablet? Check your operating system's display settings. More here: Troubleshoot computer does not detect display
If your computer does detect the display, but you still see just a back screen, shine a flashlight at your tablet's screen, and see if you can detect faint traces of the image your computer is sending. If you do see something, then this means the backlight is broken.
Unfortunately this is not an easy or cheap think to repair. Most people simply just get a new tablet or if it is under warranty have the tablet replaced.
For example, connect it to another computer or X-BOX or DVD player. If you see something, then it tells you that the pen display is capable of showing something but that the problem is somewhere else. More here: Check if the pen display works with another display output device .