I always start the light right away, I used to wait but I was unable to check one day and when I checked the next day she sprouted out and was streched out and could not even support her own weight for a week after. I filled the pot to the top and and to create supports.
Unless your on a really tight budget then having the light on is easier. Once a sprout finds light it switches from search mode to gather light mode and starts producing chlorophyll and opening its seed leaves.
Well, you have 2 options.
You can wait until your seed sprouts and as soon as it does you can then turn on your light at 50% at 60cm away min.
Or you can turn on your light after around 12 hrs after planting. But by right you are not meant to have light hit the seed at all even when it's pushing up. But once they are up it'll open.
But nah. You don't need to turn the light on until she has sprouted if you don't want to
But either way works once you have the seed under a bit of soil and it's not getting hit by the light.
Good luck pal.
Although they don't need light until they sprout, it wouldn't hurt putting the lights on to help identify and dial in any tent issues. Also, if you forget for a day or two, and they sprout, they get real leggy, real quick searching for light.