New to OOPs so need help here plzz

Question

Hi,

I am new to OOPS concept. I have created a asp.net page which is a new user registration page. At the button click i want to call a method to handle this.. I have created a class registercls in app_code folder and i want to add some methods. I have these fields like firstname,lastname,city,phone etc.. How to write a method to handle this.. At button click i want to call the method.. plzz help