Determining what you’re skilled in is largely a process of reflecting upon both your past as well as present day work experience. Consider what tasks you excell(ed) at in your current or most recent job and what skills are/were required to do so. It’s also worth talking to your current or past coworkers, analyzing your performance review(s), and reaching out to anyone else who knows you well, as other people are often able to identify positive things about us that we’re unable to perceive.