Every job is solving problems of some kind or another. Look at the individual postings and as you’re writing this ask yourself: does what I’m writing yell them how I’m going to solve the problems that this job needs solved?
That’s what people mean when they talk about selling yourself. That’s how you get someone’s attention. Look at the job posting, make a hypothesis based on available evidence, and use the job posting to tailor a cover letter for that positon.
And if you are?