Hello,
I recently bought a bonsai tree kit with 4 species of trees included. Ive successfully germinated 3 of them after soaking the seeds in water for 16 hours and they popped out of the soil within 3 weeks! Im excited but I havent been able to find any info about what I do now. Do i begin to prune now? Do I let them grow for another few months before I do? I would be very grateful for any info on maintaining my bonsais right out of the soil! The three species that have popped are :
Jacaranda Mimosifolia
Pinus aristata
Picea Mariana

And I have a Delonix Regia that has not germinated at all. It has only been about 3 weeks though and I read that It sometimes takes up to 6 weeks
thanks!

No you did not buy a bonsai tree seed kit. You bought tree seed. You are lucky to get anything to germinate, they usually do not. There is not much you can do but let them grow, and once big enough to handle pot on into larger pots. Then in about 2 or 3 years you may have something to prune. Depending on what country you are in they need to be out and hardened off. The Jacaranda is not really suitable for bonsai but the pine and spruce are.

Thank you,
And right, I wasnt aware until recently that Bonsai 'seeds' are tree seeds but Im glad to be learning. I appreciate the response and I guess my last question for now is should I use any low-nitrogen tree food for them? They are inside in The U.S. (New York) and getting indirect sunlight until I get them outside.
Thanks again
Aaron

Hard to tell. Once the trees start to bulk up, you need to replenish the nutrients in the soil. If they are very young you are probably ok. But we cannot tell what soild it is in nor whether that was nutrieent rich potting soil, or bare gravel.