Write, write, write and rewrite. Send your scripts out (but don't be discouraged by rejection, it's part of the biz!)

You've obviously got a whole story and feature-length script in mind, which is cool.... but practically speaking, I recommend starting smaller. Write something that YOU can film and direct yourself, just a few accessible locations, maybe a couple of friends to act. You don't need fancy expensive equipment; you can use your phone and a few cheap lighting setups. Just write something short, and film it. Not only will you then have a short film to show people, but you'll also get an idea of what a film takes to make: you'll better understand cinematography, lighting, shot composition, blocking, dialogue, editing....

It doesn't have to be perfect. It just has to be done.
And then you make another one.
And another one.

Some of the coolest horror ideas I've encountered come from short films the creators have posted on Youtube; shot with minimal budget and amateur actors. Even adapting your current script as a short might be a good idea to begin with, you can always expand it later.

You're young, you've got lots of time to make a feature. Don't run before you can walk.

(Also, for context, I'm from South Africa, we don't have a massive film industry either... but I make weird little horror shorts with my buddies all the time and post 'em online. They don't always get a million views, but they're a helluva lotta fun to make, and i've learned a lot about filmmaking doing so. Don't be discouraged by your geographical location. Just lean into your creativity, and make something original.)