Here's how you can turn on automatic app updates in iOS 7.
1. Go to Settings.
2. Go to iTunes & App Store.
3. In the Automatic Downloads section, toggle the App Store Updates switch to the green position (just look for the app store icon).
Automatic app updates is one of the best features in iOS 7. Once you get used to it you'll never want to manually update apps again.
Once an app is updated, you'll see it listed in the Updates tab in the App Store. So it's very easy to know which apps have been recently updated on your iOS 7 device.