So now you'll learn... It's brave and smart to admit something like this and to be open to improving. Did you know there's a group on JobCase about resumes, cover letters and interviews? (See https://www.jobcase.com/groups/f523c8c8-eecb-498b-aea0-9250c6cdf9c7) There are also many good examples on the Internet. Do a few searches. Some of the most common suggestions I've seen boil down to

• use a formal letter format
• 1st paragraph tell them which job you are applying for (and maybe why at a high level you are a good match)
• 2nd paragraph give examples of your accomplishments or where you've demonstrated the kind of skills they need
• 3rd paragraph close with a request to interview (or whatever your next desired step is), and if you can, say how you would help them
• put your contact information on both your cover letter and resume in case they get separated Some companies/recruiters find the cover note highly valuable, and others claim they won't even read it. Good luck!