Would most appreciate any pointers to allow me engage first gear before the starting red lights turns off in a race.

I have a clutch paddle and use the paddle shifter on my steering wheel to shift.
At the start of the race, before the red lights goes out, I would push down the clutch and flip the shifter to put the car into first gear. It doesn't do anything, car stays in neutral.

I know this is possible, because some of the people I race with do that. In replay I can also see they have first gear engaged before the start light goes out. When I ask them how they got it working, they told me it just works for them.

I am really puzzled. And this makes a big difference in a race. Those who can select first gear before the light will always beat me at the start