If Prime Now delivers to your area, you get the option to sign in or browse as guest. We choose to browse as guest here.
Here you can browse a feed of categories, select local stores to shop at, or search for items.
There's also a "deals" section under the search bar that shows what offers are currently available.
In the shopping basket, you can review your items, or continue by signing in with Amazon You can't actually sign up to a Prime account in the app, so you have to have one already.
If you have less than $20 worth of items in your basket, you can't proceed. You're given the amount you need to add to your basket to reach $20 and there's a big "Add more items" button.
Once your basket is full, the message about needing to order more than $20 worth of items is gone and there's now a Checkout option.
After clicking the Checkout button, you can select your shipping preferences, then, complete your order.