This letter would be addressed to a HR person in any organization that has published advertisement for job opening. The cover letter template should contain details about the source you came to about the job, your academic qualification, your work experience relating the vacant position and your reason for joining the firm.
Subject: (The post applied for)
Dear Mr. _____________
Here you must mention the source through you which came to know about the job opening. You must explain why you want to join the company. The first paragraph should be writer well and it should compel the reader to read further.
Here you must mention your educational qualification and your work experience related to the job opening. You mention your academic, other qualifications (if any) and other personal traits and your past achievements that would develop a positive image of you in the minds of the reader. Keep the paragraph short and precise.
Here thank the reader for their time to consider you application and make polite request for an interview schedule with them.
(Name and Signature)