Enter the Circle-Open PK -
Find Captain He (101,88) in Water City. Speak to him, he will give you a dart.
Take the dart to General Cai (31,88) in Water City, right click on him, then
click on "All right", you will enter into fighting his level-20 detectives.
After you defeat his detectives, he will issue a PK license to you, that means
you enter the Kungfu Circle from now on.