Some advise from a person who has helped teach a few kids over his life;
Read, read, read ... everything you can - Re-read the things that appeal to you. The stickies on this site, and the vast array of tutorials that can be found online ( search "Knife Tutorial") will take months to tears to read them all. Go to,the local libraries and check out every book on blacksmithing and knifemaking. There are good books and DVDs available from many sources, there is a list in the stickies.
Here are a few tutorial links:
http://gbrannon.bizhat.com/instructionallinks.htm
http://gbrannon.bizhat.com/multipletutorials.htm
http://www.knivesby.com/knifemaking.html
Start slow - No one should expect to go from first knife to a katana in a short time. It takes a lot of practice and a lot of hard work.....sometime years of it.
Build up to a full shop - Make and get equipment as you need it. Tools don't make good knives....trained hands make good knives.
Get your folks on board - You are 15. While that feels totally independent, it isn't ( hard fact). With your folks cooperation, you can attend nearby knife shows, hammer-ins, do some shop visits, and get some tools and stuff. No maker is going to invite a 15 year old to his shop unless accompanied by a family member. When your folks see that you are willing to study, be mature, and devote yourself to a project and see it through, they will be supportive.
Knife styles - While Zombie slashers, big camp bowies, and long daggers are neat, a 3" blade drop point hunter or a simple kitchen knife would be both useful and also give better impression of you to adults that you will need the cooperation and support of. The will also be far easier to make and come out good looking.
Don't get discouraged - There will be delays, failures, nay-sayers, and just plain "stuff" that happens to slow you down. Take it all as part of life and part of learning.
Set up a little place to work, and keep it neat - This is covered in the tutorial "How to Instructions for making a Knife)
http://www.bladeforums.com/forums/showthread.php/694673-How-to-instructions-for-making-a-knife
Use this search engine for looking up info;
http://www.google.com/cse/home?cx=011197018607028182644:qfobr3dlcra
You just missed this years show, but get with the assn. and find out about other meetings and events;
http://www.floridaknifemakers.org/