Hello this is my first post, and so a greeting is dutiful. I tried to make my lcd 16x2 kit work with the example sketch but neither does the screen turn on. should be enough pin 1 GD pin2 Vcc 5V pin3 a reference voltage between 0//5V for contrast and the screen you should turn on. Pin 4 on d12 Pin5 GD pin 6 (E) d11 pin 11 d5 pin 12 d4 pin 13 d3 pin 14 d2. Not work help me .
Thanks
Let's have a picture of what you are doing. That may sort out something obvious. 
Actually, you don't mention connecting the backlight LED on pins 15 and 16. If you have a common "1602" display with resistor R8 being "101" which is 100 Ohms, you do not need a resistor in series, just connect pin 16 to ground and pin 15 to 5 V.
If this fixes the lighting problem see how you go from there. You need to set the contrast - pin 3 should connect to ground through a potentiometer but the potentiometer should not - despite what you may read - connect to 5 V. A 1k potentiometer would be best; if you have a 10k then it is easiest to connect the wiper to pin 3 and both ends to ground.
Tell us how you go from there. 
I attach wiring diagram and photos of the display.
The sketch is the example of the liquid crystal library. It is compiled and regularly uploaded to arduino uno. But nothing appears on the LCD only the backlight.
OK, so you have the backlight.
Next step is the contrast adjustment. First note my previous comments about the long-standing errors in the circuit you have shown. It is not the present problem but I suggest it will make it easier if you fix the wiring to the contrast potentiometer and then adjust it so you see something on the display - either the message your expect or at least, a row of "blocks" on the first line. If nothing at all happens, then your wiring is bad.
I adjusted the contrast with a 10 k potentiometer at about 3.5 V on pin 3. but nothing
If you have 3.5 V on pin 3 with respect to ground, you have almost certainly not followed my advice and have made a bad wiring blunder.
Since I cannot see your wiring, I cannot tell what the error is.