It's a "play-date" ask her if she has anything to do. If she says no then accept it. Don't write a note or send her a text, we hate that. Be forward.
Well, for starters don't call it a "play-date" unless you're both under about 3 years old.
Just how you get a date with any other girl-ask her out.
ask her to go out with u
You ask her out.
== ==
ask her!
ask Her on a date
you ask her?...Or you ask her best friend if she likes you and is she allowed to date.
Ask her out.
If you can date, ask her out.
ask her on a date
On the date? Ask her about herself.
Ask her out on a date.