When speaking of authorities, the first things that come to mind are your employer, the officers in the legal system, or perhaps a guru; or, if you're young enough, teachers and parents. Authorities are the people whose command you obey without questioning, and whose opinion you value maybe even more than your own. In your mind, they are somehow above you. But there's no reason you couldn't be considering a random stranger, for example a social media influencer, an authority. Or a fictional character in your favorite book. Or a close friend. And this is where it gets tricky.
What made you consider that particular person an authority? Or was the process completely unconscious? Maybe you can't tell why you place someone else's opinion above yours.
I urge you to think about this: list people whose opinion you value or whose commands you obey, and think about why you respect them so much. In the case of an employer the answer might be easy (to get paid), but what about your friends? How are their opinions better than yours? And if you consider your parents authorities still in your adulthood, is it because you genuinely respect their opinion while making your own decisions, or have you never learned to think on your own?
'Place nothing above the verdict of your own mind,' Ayn Rand said. And while Rand wasn't right about everything, I think she was right about this.
It's your life. You govern it. You have the freedom, you face the consequences.
You are the authority.