Opening the first few sentences of your cover letter should tell the reviewer which job you are applying for and the connection you have to the company. If someone the reviewer knows suggested you apply, mention that recommendation. If you are responding to an advertisement, refer to it and the source that published it. Your knowledge of the company might give you another opportunity to connect your self to the job. You could briefly describe your experience with its porduct scite a recent company success, or refer to an article written about the company. But don't go overboard: save specifics for the interview.
Body The next portion of your cover letter is a brief is a brief explanation of your qualification.