After planting germinated seed, when do you add light?!

I would greatly appreciate any help with this first time grow.

After planting germinated seed in soil, when do you add light?!

I have pre-moistened my soil, and planted my seed in root down in a plain red plastic cup.
The root was this long ( ------ ) and I planted it in the soil just barely covering the top head of the seed.

- I was told to keep the cup in a warm, dark place and cover with saran wrap after dropping in the seed. This will make the seed shoot above soil, then wait until the leaves show and place under my 600 w MH light about 6 ft under. Is this the correct way to do this? Or do I put this seed directly under the light?! I currently have the cup covered with saran wrap and a next to a heater in a dark room..... should this be under light?

I can't figure this out and am reaching out in the forums as a last effort! Much much appreciated. I have some pictures of my setup.

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It needs light as soon as you stick it in the soil. If you use the 600w make sure you it way above the seed till it gets well established. Just a few clf bulbs work very good for starting seeds.

Thanks.