I’m in need of advice

Hello reddit, this is my first ever post, but since I have no idea where else to ask I’ve decided to take a shot right here.

u see, I have a crush on this girl, she’s about a year younger (I’m 26) than me and I’ve known het for about 15 years. At first I didn’t think much of her as I was more interested in her twin sister and she was friends with my younger sister (whom I despised) so I never talked to her all that much, after that because of the fact that I had to live in a Boarding school for some years so we lost touch.

But about 9 years ago I met her again at sailing camp and I have to say that I immediately fell for her (she is goth, nerdy, a metalhead, loves animals and she’s straight up gorgeous), but as she had a boyfriend at the time and I was kind of seeing a girl (complicated), I didn’t try anything and we fell out of touch again.

later on we met again since we were part of the same friend group and we got along quite well since we have similar interests, but then she once again got a boyfriend and she stopped coming to our outings. so we once again lost touch.

I’ve dated a couple girls in this timeframe but none stuck.

so now on to my current situation, I want to try talking to her via Facebook or something and then ask her if she wants to hang out, I know for a fact she’s single as a mutual friend told me. However here is the thing, I’m Autistic and partially because of that, and mostly a lot of bullying, I am socially inept, I have no idea how to take this step, what to say to her or whatever the fuck. so I came here to ask for any semblance of advice.

So reddit…. please help me….