help please 250watts hps

as close as possible. hold the back of your hand where the top of your plant will be, if after a minute it is not uncomfortabley warm you are ok. if not raise the light a bit and try again until you find where you are ok.

Agreed, the hand burn test is the best subjective way to find the sweet spot but I will add to get some yoyos as clones or seedlings coming from fluros or CFL will burn. Start with the light up as high as possible on day 1 and move it down to the sweet spot a few inches a day and then move it back up to keep it at the same distance as she grows or hold her down with ties or screens!
Peace