Set up your letter, following conventional letter format. Type the date in the upper left-hand corner of the page. Below the date, include the organization's name, then the recipient's name, and then the organization's address. Just below this address block, type "Re: Letter of Intent." This signals the formality of your statement of intent and at the same time clarifies the purpose of the letter.
Add a salutation, such as "Dear," followed by the recipient's name. Add an honorific, like Mr. or Ms., and don't forget to include any titles or distinctions that may apply, such as PhD. or J.D. After the person's name, type a colon, which is more business-like than the more informal comma.
Insert your statement of intent essay. This will be the body of the letter. You may need to tweak the tone of your essay to make it more appropriate for the letter format. Your essay may consist of relatively impersonal language, but for your letter, you will want to make it sound more personal, so that the recipient feels as if you are directly addressing him or her.
Edit the essay so that it fits the constraints of the letter. If the institution suggest that you send them a letter that is two-pages long, stick to this requirement.
Divide the essay into three parts and arrange it accordingly. In your opening paragraph, include the parts of the statement that convey your purpose for writing the letter. The second paragraph should include the parts of your statement where you provide examples supporting your intention, and the third paragraph should include the parts of your statement that describe your goals and how you want to accomplish them.
Close the letter by emphasizing your enthusiasm and your desire to speak to or further correspond with the recipient. Try to end with an action statement, such as, "I look forward to speaking with you regarding the opportunity to enroll at University X." Print the letter on letterhead stationery, if you have access to it.