You need to do a significant amount of research and talk to your parents about it. Since you intend on selling online-you're going have to learn about SEO (search engine optimization) as you can't just put your items up for sell and expect for customers to come, you have to persuade people why they should buy from you and you have to let people know that you're there. You also are going have to learn about pricing, branding, marketing, taxes (your parents will probaby have to fill these for you), etc. It really is a lot to take in, but many of my resources say that starting is the most difficult part. Books, google, etc can only teach you so much (but you still should start there)-you learn the most by doing and making the items is often the easy part.
Your age might would interfere with you being able to start your business legimiately, as you will need licences and permits-which varies by state and city. In some cases-this can be quite expensive as well. In my area, a seller's permit costs $500. Your parents should be supportive though -so try to see if they can help out.
You already have the idea, now you just need to do the research to determine if the idea is feasible.