Annabelle,
The main things you need to consider registering for are sales taxes and employment taxes (if you intend to have any actual employees). As a seller of a physical product, you will be considered a vendor in sales tax law, and, depending on how much business you can and where it is shipped, may be required to collect sales tax and remit it to the state government. Similarly, if you have any employees, you generally are required to collect and remit withholding taxes, in addition to paying the employer's portion of the payroll taxes. Depending on where you are running this business, you may also need a local business license. That depends on several factors, including the county or city in which you are doing business, the size of your operation in terms of employees, and whether the business is being operated out of your personal residence.