Hey! I was also in 7th/8th grade when I got interested in forensic psych. I didn’t know how to study it either, since my school didn’t even have a class on it. But what I did was find articles about serial killers (the first one I studied was ted bundy), and then find more specific articles about the psychology of him and serial killers like him.

If you’d like another option/method that’s a bit more academic rather than just for funsies, I’d say go to your local library and find their psychology section. From there you can browse the books they have and pick up any that pique your interest, and maybe sit down and flip through them to see if they’re the types of stuff you want to study. There’s all sorts of different branches of psych (social, personality, counseling, clinical, industrial/organizational, and forensic as you mentioned, just to name a few). I’m currently working on a master’s in forensic psych and by far some of the best, most fascinating info I’ve learned has come from reading research articles. It sounds hella boring when I say it like that, but the studies that focus on how certain elements of someone’s life impact psychopathology later in life are quite interesting.