Row Column Scanning Tutorial (12v led)

but how does that even work? i have the uln2803 which sinks the current, i can't put that on the anodes, i can't just wire them to 12v, as then i dont have control of them.

disregarding the row control, i currently have;

12v > leds > uln2803 with the outputs going to the arduino, and pin 9 to ground and pin 10 to +ve

connecting anything to pin 10 doesnt actually do anything, gnd / +ve / not connected same result

all i can get these lights to do is partially light up, some columns at full brightness, some at half...

i know all the leds are working fine, and it is the way i have it connected, but im actually lost now! i think 6 hours of poking this chip is melting my brain!