Now that you have your FID, you can proceed onward to what makes your business an official corporation. File articles of incorporation with your state's secretary of state. Massachusetts entrepreneurs can file online here. Note, too that you do not necessarily have to reside in the state you incorporate in. Many people incorporate in Delaware due to low initial cost and other benefits. A quick google on the subject led me to a few helpful bullet points. I opted to incorporate in MA for convenience and to support my local economy.
Name your Officers
When filling out the Articles, be sure to name all the important officers of the company - namely your President, Treasurer, and Secretary. It varies by state, but most states allow you to hold all three positions.
Allocate your stock
Assign stock to your board of directors and other interested parties. This part is tricky and generally completed with the help of a good attorney. Since I'm the only member of the board at Enlight Solutions, it was easy for me. I issued 200,000 shares of common, no par stock worth $0 to myself. There are two classes of stock: common and preferred. Usually, common stock gives the board member voting rights whereas preferred stock gives extra benefits such as dividends in exchange for voting privileges. (More formal definitions can be found can be found here)
Pay your fee
You have to spend money to make money! It's cliche, but in this case it's quite literal. You can't legally file your companies taxes without submitting your articles. In Massachusetts, it costs $265 in filing fees to process your articles. Be prepared to remit payment so you can be up and running quickly.
Legal Eye for the Business Guy (or Girl)
Make sure to have all of this looked at by an attorney that is well versed in business law before you actually submit your articles. A trip up in these early stages could lead to serious problems down the line.
Your articles of Incorporation are public information. You can search MA filings here. You can use other corporations filings as a guide to help you.