Go to one of the job related web sites (monster.com, acm.org, etc.) and select a job that best fits your education and experience. Print the job description. Your assignment is to write a cover letter for that position. There are many different places that you can go to find help with your cover letter. There are numerous web sites that provide sufficient details on how to write a cover letter. You need to submit the guidelines that you have used for writing the cover letter. For example, the few pages that you have used from a web site or from a book.
Here is what you need to submit:
1) Your cover letter without spelling and grammatical errors. Remember that this letter along with your resume is the only thing that an employer will see from you. Thus, this letter must represent you very well. Be sure to read the letter several times to make sure it is free of error and that it clearly says what you wanted to say.
2) The job advertisement (job description)
3) The resource that you have used to write your letter. If it is a web page, prints the few pages that you have used. If that is a book, reference the book and write the page numbers that you have used.