Hi Hexley,
attached a photo that shows how I supplied the display with power.
The regulator U701 gets 12V DC on its input and outputs 5V DC. Pin 1 is the input (+12V), pin 2 is GND, the unconnected pin 3 is +5V.
I simply routed a cable from the AC connector of the new display to the regulator pin 1 and 2. As my display design has a bridge rectifier on its input, it does not matter where you connect +12V or GND to.
Best regards,
Kai
PS: The displays I bought are sold as white on black displays, but actually they look a bit blueish as you can see on the pictures.