For most people, through professional help. You aren’t SOL, and you could get there yourself, but it will be far easier with assistance from medical and psychological professionals that are trained to help guide you in ways that aren’t just you struggling on your own or beating yourself up internally.

I’ve skimmed your other posts and you need more than well meaning strangers on the internet will be able to give you. You may also want to look into potential legal action against the institution you say you were stuck in, as none of what you described sounds like standard practice of care for the autism misdiagnosis you said put you in there.