It looks like you have PiScreen connected correctly.
On one side of PiScreen, there is a on/off switch that turns the backlight on or off. I see that in your photo that it is ‘on’.
I would say the problem is that you need to install drivers.
If you follow the links below, they will definitely help you learn how it all works.
Driver install Instructions here;
Once you get the drivers installed, you should do these also;
Mark --OzzMaker.com --