The Takarazuka theater is located near Yurakucho station and tickets can be purchased at most convenience stores.
Takarazuka is originated in Takarazuka, Hyogo prefecture. You can see shows in Tokyo Takarazuka Theater near Yurakutyo station. It takes five minutes from there.
You can buy tickets from online site. However, it does not have English site, so you can simply visit the theater and purchase tickets. Almost every day they have a show.
If you REALLY love Takarazuka and want to see the original theater, you can go to Takarazuka, Hyogo prefecture. It only takes four hours from Tokyo station. You can check the train from this link: http://www.jreast.co.jp/e/index.html