Your cover letter is an introduction of yourself and an argument for why you are the best candidate for their company and the specific position
The cover letter should be addressed to the hiring manager and should include one paragraph with the reasons you think you are a good candidate and two or three major accomplishments that are related to the position advertised
The inclusion of comparable accomplishments should increase your chances of getting an interview. Make sure that it is easy on the eyes, for him/her to find the information you want to highlight