Co2 and basic grow room advice needed!!!

HI all, i currently invested in a co2 tank, regulator, and co2 test vials. I am wondering what exactly do i do. Do i turn on the exhaust for so long then when that goes off have my co2 turn on? How long do i run my exhaust? Anything you guys can tell me would be greatly appreciated. Also, i have a nutradip trimeter and i cannot use it when my lights are on because of the rf interference, so i run a green light to check my resevoir and fill it up when needed. My question is, im 2 and a half weeks into budding and only some of my plants are budded heavily, is this normal? Does the green light affect this, i was told it doesnt, but im not so sure anymore. Thank you for your help everyone.