Hi Gladmar; welcome to The Passion. I don't know how much you know about growing your own MJ so I will give you some basics. First, MJ is a very high energy plant that requires a lot of light energy to properly do its thing. That said, you need to decide how and where you want to grow your plants. If you want to grow indoors then you need to be getting a good high powered florescent light that emits around the 6500Kelvin spectrum of light. This is what the MJ plants grow best under (aside from the sun).
Now the lights take up a given amount of space and will put out light in a "foot print" that can be somewhat bigger than the size of the light fixture or about the same size as the light ffixture. You will need to decide on a place to grow your plant within your building of choice. You don't want to have a plant under a single light that is suited ffor a 4square foot space in a room that is 10'x10' where the light can disperse around the room. Ideally you want to have a dedicated space that can be closed in so that the light energy can be contained over the plant so that it gets the most that it can.
The actual lighting requirements for MJ is a minimum of 3000 lumens per sqft during the vegging period, and a minimum of 5000 lumens per sqft during the flowering period. This would equate to a T5 florescent light fixture that is 4' long and has 8-12 bulbs to properly light a 4'x4' space during the veg period. Many of us use HPS for flowering because it puts out high intensity ~3000K spectrum which is ideal for flowering. The 600w HPS is ideal for flowering in a 4'x4' space.
It appears that you are growing yours in coco coir or some similar synthetic medium as opposed to regular soil. That is not a problem. I use coco coir myself and love it. However, using soilless medium to grow in requires a few things to be done a little differently. These mediums have little or no nutrients for the plants to draw from so you will have to feed them on a regular basis. I highly recommend that you look at some of the MJ formulated nutrients. General Hydroponics has a very good 3 part nutrient called Flora 3 part. It is ffairly easy to work with and the MJ plants do quite well with it. If you are at all experienced then you can choose what ever you want but if you aren't experienced then I would highly recommend you get the Flora.
For right now, you have a seedling and it needs very special care. First, don't over water or try to feed it. Both of those things will kill your seedlings. The seedling only needs the medium to be slightly moist. Anymore than that will kill it. DO NOT FEED IT YET. As the medium begins to get dry around the seedling, give it about 10ml of water with NO nutrients in it. You will watch your seedling for about 2 weeks. It has 2 tiny round leaves that will emerge ffirst. These are the "Cotyledons" and they are the food for the seedling while it grows its roots.
Once it has used up the nutrients in the cotyledons, they will begin to get yellow. By that point you should already have at least 1-2 pairs of true leaves. When you see the cotyledons get yellow then it is time to begin ffeeding the plants. You will begin with small amounts (about 1/4 of the full strength dose that is recommended on the bottles). For the first 2 feedings, you will use this dose and then each week after, you will increase the dose to 1/2, then 3/4 then full strength by the 5-6th week of life.
There is much more to know and I am certain others will chime in with tips and important steps to take. If you have any questions, just ask, but I also recommend that you do some serious reading on your own. First read all of the stickies at the beginning of each thread that is important to you. Breeding is not an important thread ffor you now if you are inexperienced. But we will try to help you. If you post a question and no body answers right away, please be patient as we all get busy sometimes with our own stuff or with helping others. If you don't get a response, please don't post the same questions in multiple threads. instead just PM me or one of the mods and we will get back to you as soon as we can