How do you turn a product idea into a real business, from developing the product to finding investors and selling it?

I am a high school junior interested in industrial design and entrepreneurship. My long-term goal is to create my own product-based business. Sometimes I think of product ideas that I believe could have potential, but I don't know what the process looks like after having the idea. I want to understand how entrepreneurs develop and test a product, determine whether people actually want it, create a business around it, find manufacturers, handle things like funding and intellectual property, and eventually present the idea to investors. I would especially like to hear how you approached these steps when building your own business and what you would recommend to someone starting from zero.