If you are non-Japanese, Kyoto is a hard environment to enter into because they are still fiercely traditional. You’re better off trying your chances in other places like Tokyo who are more lenient towards accepting foreigners. To do this, you can apply to an okiya yourself through phone or email, but it will be a lot better if you know someone who can introduce you to an okasan or a mother of an okiya/geisha house. Speaking of which, do NOT try to apply if you don’t know how to speak the Japanese language yet; otherwise, absolutely no okiya will take you!