There's really no one, simple answer to that. But here are a few thoughts:
1. Make sure your work is as good as can be. Whatever is the best way for you to learn - classes, books, YouTube videos, whatever - do it. Then do it more.
2. When you believe your work is really good, consider submitting to some high quality screenwriting competitions. Placing well in something like Nicholls will definitely get you noticed.
3. Consider submitting to competitions that are associated with film festivals. If your work is an official selection or award winner, go to the festival and network with other writers and - even more importantly - with filmmakers who might be interested in teaming up with a promising new writer (this is mostly for when we're at least somewhat back to normal and festival are again in person events).
4. Team up with an aspiring director, dp, actors, etc and produce your own work. Then get it out to the world as much as you can - which is not easy. Festivals, youtube, vimeo - whatever. Keep pushing and keep promoting.