In order to start a business, the first thing you'll need to do is figure out what problem you are trying to solve. Every business makes money by solving a problem that their customers have. So if you're opening a restaurant, you're selling food to hungry people. If it's a smartphone app, you're hopefully solving a problem that smartphone owners have. By finding a problem that you'd like to solve, you can identify what you want to start your business around.
The next step would be to figure out what skills would be needed to make this business a reality. Do you need to know anything particular for that industry? Are you going to need a business partner to help you figure things out?
The third step would be to start talking to people in the industry you're looking to enter to find out as much you can about it.
Only then would I start looking at the steps to forming a business (incorporation, hiring people, selling products, marketing, etc.)
There are many more steps, some of which will be very specific to the industry you want to start a business in. There are tons of books and websites and people to help out with each of these steps. It can be very tough to start a business, but a lot of people loving doing it. Best of luck!