You should be able to find a format online, but the letter should include who you are (briefly), why you are applying, what your utlimate goals are, and how you would fit in or be the best match for whatever you are applying for. These are usually one page summaries, that are succinct and should be interesting or attention getting without crossing the line of being too weird (meaning be original). They usually make you write a LOI and then attach your CV to it when you are applying for leadership positions, jobs, residency, etc. Don't include your CV or resume unless they ask ofr it though...
