First, welcome to the site. I hardly know where to begin, these kits are a detriment to aspiring bonsai enthusiasts and should be shunned by all.
They are marketed to the unwary, supplied with ill conceived directions, inferior materials, and seem almost designed to fail. It's not your fault but I have little hope for this particular seedling.
Pines are not suited to indoor culture and should be outside 24/7 in most locations. The soil supplied is very peaty and ill suited to your purpose. Never let it stand in water, as shown, for more than a few minutes. Light behind a window is greatly diminished and inadequate for most species. Even if you nurse it through its infancy it requires a dormant period during winter and will need to be hardened off. Sorry I can't be more optimistic.
The good news is it's only one and if you are serious we can help with your future endeavors. If you wish to pursue bonsai further we can continue, perhaps in a new thread.