Seems like I don't have the option to choose portrait, nor do I have the option to change exposure, is this a guide for all iPhone 7's or just the iPhone 7 plus?!
EDIT: Everything else in that guide should work on the normal iPhone 7. Most of the guides work with older iPhones too.
When you tap to focus on an item, the box should appear with a sun beside it, you can draw your finger up to increase the exposure, you'll see the sun move up in relation to the box.