First go to your notes app and open up a new note. Make sure there isn't anything typed in the note already.
Now that you're in the app, type what you want to say.
Turn on VoiceOver. If you're not sure how, it is in the Accessibility area in your Settings app.
VoiceOver will automatically say what you typed, as long as it has correct spelling. Make sure you turn VoiceOver off before you start typing again. It gets difficult if you have it on.