Summarize the following:
It's the app with the multi-colored pinwheel. If you don't have Google Photos you can download it from the App Store and sign in with your Google account. Scroll through the "Photos" tab to find the picture you want to upload and then tap it to select it. This opens the photo or video in a preview window. To select multiple items, long-press on a photo and then tap the other items you want to select. Photos or videos that are not already uploaded will have a cloud symbol with a line through it in the bottom-right corner {"smallUrl":"https:\/\/www.wikihow.com\/images\/9\/9e\/Android7cloudoff.png","bigUrl":"\/images\/thumb\/9\/9e\/Android7cloudoff.png\/30px-Android7cloudoff.png","smallWidth":460,"smallHeight":460,"bigWidth":"30","bigHeight":"30","licensing":"<div class=\"mw-parser-output\"><p>I edited this screenshot of an Android icon.\n<\/p><p>License: <a rel=\"nofollow\" class=\"external text\" href=\"http:\/\/en.wikipedia.org\/wiki\/Fair_use\">Fair Use<\/a><br>\n<\/p><\/div>"}. It's in the top-right of the screen. This opens a pop-up menu at the bottom of the screen. It's at the top of the pop-up menu. The photo or video you selected will be uploaded to your Google Photos account.

Summary:
Open Google Photos. Tap a photo. Tap ⋯. Tap Back up.