How do I reset my iPhone to factory settings

Settings>General>Resets>Erase All Content and Settings

Thank you soooooo much. So simple.

Will I be able to restore it from itunes if it's been backed up?

Thank you

Greetings,

I already did this but AT&T said on the phone when I unlocked it that it had to be done through iTunes.

Am I misinformed and is this all that I need to do?

Thanks in advance!

In order to complete an unlock, you must restore the phone using iTunes. All the above does is erase all of the content and configuration settings from the phone and put it back to an as-new state.

Unlocking requires that changes be made to the phone that require a restoration using iTunes.

passcode has me completely locked out from any settings

Perhaps you'd like to explain this?