How do I flirt? I have no idea how to do it. And how do I know

Just watch youtube videos or romcoms. It's pretty much being fun, clever, and teasing. Try to touch an arm or leg so she remembers you.

Bumpu

what i experienced was that being very open about things was seen as flirting. Maybe it helps?

I don't know the subtleties but I know you have to look them in the eye when you talk. Took me a lot of practice, but they reciprocate if they're interested. If they're not, they'll keep looking away, unless they're shy also. But you should detect that beforehand anyway.