how do I walk up to someone and talk to them?

I’ve been talking to this girl from my school quite a lot online, to the point where we had a late night talk where she told me she wants to talk to me irl but she has social anxiety so she can’t just come up to me. I am worried if I don’t do anything we won’t get to the point of talking at school as friends but I have autism and I’ve never just walked up to someone and spoke to them. any advice on what I should do/say, and how to carry an alright first conversation?