I have a small store in Yahoo, but would like to become an official small business owner. This way, I can register to receive credit card payments online and have the company officially registered. For this, I need to have business owner information and a business social security number. I have no idea where to start all of this!

Also, which state should I try to register my business in since it is online?? Any advice?

Register your store name as an assumed business name in the state/county of your residence. Then apply to the IRS for a federal tax ID number.