First check the button by the display, give it a good press. If nothing shows you'll need to get the batteries replaced before you go any further. If the display shows then you'll need to adjust the reg.
There's a grub screw in the end of the reg, this needs to be screwed with a 2.5mm allen key, to increase the pressure. When you're ready to do this, press the button on the reg, that's in the bottom right corner of the display, and it will show the pressure in the tank. Press it two more times and you will be shown the output pressure. While the display is showing "output pressure" turn the allen key so that the screw goes in, and you will see the display increase until you get to the required pressure. If the display goes out press the button again until you get to the output pressure display.