becoming a GCSE tutor

I recently recieved a 9 and an 8 in my GCSE combined science, and I am considering trying to get a tutoring job when I start year 12.
I am also about to begin studies in Biology and Chemistry A levels so I am hoping that may make me seem like more of a trustworthy person that people could pay money for.
However, I have no idea how to start and how exactly I would do it so if anyone has any advice I would much appreciate it.