To legally register a business as a 15-year-old, it will require the presence of a legal guardian to act as a trustee or a custodian of the business. As a teenager, choosing one of your guardians or a legal representative to do this gives you the freedom to focus on building a brand on social media and growing it with all the legal work in the background handled by an adult who is required to hand over complete control once you hit 18 years.
One step a 15 year old would need to take to legitimately start their own business is to research the legal requirements for setting up a business in their state or country. They may need to obtain a business license, register the business with the local or state government, and/or obtain any necessary permits or licenses. Additionally, they should consider researching any applicable taxes that may need to be paid, and look into insurance options to protect their business. Finally, they should create a business plan that outlines their goals and strategies for running the business.