Pitting during the race

I was in the beggining of the race and the green button in the bottom of the screen started to say "pitting", I thought that the car needed to go to pit stop and I clicked. After that the car retired of the race. How should I procede during race? Does it pit automatically or I have to interact? Thanks.

were you using 2d or live timing? it will automatically pit once you are running low on fuel [i.e not enough to finish a futher lap], so the box goes green to indicate you are pitting[then grey to in pits], if you clicked this again you will have cancelled the pit stop for 1 further lap and subsuquently ran out of fuel

I was in live timing. Thank you David and Nico. I got it now.