How do I officially quit Catholicism?

[FirstLast]

I was baptized when I was only a few months old. Obviously, I was not able to think for myself yet at that time.
Growing up, I never really believed in any god and questioned many things about religion.
Most of my friends already know what I believe in. They already know I'm an atheist, although we still do not agree in each other's views.

I just want to know how I officially quit the Catholic Church.

 

[Thisismyavatar]

Flash a nun or get an abortion, that will get you excommunicated in no time.