How do I turn off passcode?

To turn off the passcode go to settings then scroll down to Touch id and passcode and enter in your passcode as prompted then scroll down again and select turn off passcode

Keep in mind if you don't use a Passcode on your iPhone and your lose or your iPhone is stolen, whoever comes in possession of it, will have full access to all your data on your iPhone. It is NOT recommended you stop using a passcode, but if your data isn't all that valuable and you wouldn't mind if someone can access it, that's entirely up to you.