Register your T-shirt business with your city and state offices. You will also have to apply for the licenses that your state requires for a T-shirt business. You could use your name as the name of the business, if you are will operate as the sole owner, or register a DBA (Doing Business As). Design some T-shirts.f you plan to have others implement your designs, then you would need a graphic designer, a printer and a source of T-shirt blanks. Prepare a business plan. This is a formal statement of your business goals and how you plan to run your business to achieve them.