How do you obscure text in a password field in an iPhone Application?

I don’t really understand your question, but I’m guessing you want a UITextField which displays dots for the characters, which every password field on the iPhone does. For this, you want to set the secureTextEntry property of that UITextField (UITextField has such a property because it conforms to the UITextInputTraits protocol) to YES:

textfield.secureTextEntry = YES;