To use the shortcuts in Setting, Head to Settings.app > General > Keyboard > Shortcuts.
Then designate a specific set of characters, preferably ones that don't correlate to standard languages or typing. For me, I set my email using the shortcut named "E16Z" You normally don't type E16Z so it won't randomly crop up when you're typing or mistype.
Phrase would be filled in with your email, shortcut would be filled in with a set of characters or symbols. Once you type out that specific set of symbols or letters, your email will show up instead.