How do i show my interest back to a girl who is interested in me.

I am so sad man.. This happened for the fourth time this year. A girl was looking at me again and again. I was talking to my friend, she made a long eye contact with me and i chickened out and quickly looked away towards my friend. The next time she gave me an angry sideeye when i crossed paths with her. I am autistic and don't know how to reciprocate the interest back. I wanted to talk to her but couldn't yet again and now she definitely hates me. She tried to maintain eye contact 2-3 times and I looked away everytime as i didn't know what to do. I really liked her and I f**ed up again. I'm gonna die single/virgin at this rate.