Well, what you need to do when you write an application letter is first introduce yourself in the first paragraph and tell the CEO what position you are applying for. In the body paragraph, you need to present yourself and your skills, and tell the employer what it is that you have to offer him and why they should pick you for the job. Reference your resume here, but don't repeat it. In the end, you should thank the CEO for the opportunity and let them know you are waiting for their response.
Hope this helps! :)
