First you need to validated your idea come up with a minimum viable product. Do a video of you explaining your product idea and start to gain potential customers and validation prior to investing in a idea you can also pivot as you begin to get feedback from early adopters. Go speak to people and ask them of their opinion – not family or friends.
After you have some understanding of your market the next step is to get your physical product designed. Chinese manufacturer or prototyping shops require technical drawings with a bill of materials to be able to product the prototypes.
Also between prototyping and shipping to customers is a process know as Dfm (Design for manufacturing) this process makes your prototype manufacturable. We try to reduce material useage, find better processes to product your product reducing costs and keeping the products specification and performance intact