I connect 2 red wires to the female barrel jack, correct or not.
Then connected 1 red wire to the arduino 5v, and the other red wire to the display. If the first one is not correct then this wil be also
I connected the black gnd wire from the female barrel jack to the gnd pin / socket on the arduino
Then I connected the male barrel kack of the 6v power supply and hoped. The display flashed on, then off .
Thanks