How to add ringtones to my iphone 4?

I need some help can anyone guide me step by step on how i can add ringtones to my iphone 4 Please
no rudeness & thank you to the ones that help

Well if you want to buy some, go to the iTunes store, and search up an artist. For example "britney spears" then there should be a ringtones section and just press buy. If you want to change it to the free ones, go to "SETTINGS" and go to "SOUND". Press ringtone and select one. Hope this helped.