If you don’t back up your photos to Google Photos, a persistent banner at the top of the UI will prompt you to “Unlock the power of Google Photos.” When you tap it, you’ll be taken to a page that includes a checklist. There will be three features to enable on the checklist. The first will backup your photos, the second will turn on notifications, and the third will sign you into Google Photos. If you already have these enabled, they will appear as checkmarks.