Once you learn to open the App bar from the left edge of the screen, you can swipe-navigate to the App screen. At top are the running apps, which display live previews; touch and hold to get the X icon to quit any (as in iOS), as shown at right. Below are icons of frequently used apps, and below that is a list of all installed apps, as shown at left.
To quickly change to other screens, drag the screen until the quick-switch bar appears at bottom (shown at left), then tap the desired screen: Music, Home, Apps, or Video. (The Home screen shows frequently used apps, recent videos, and recent music.) You can also swipe sideways to move among open screens.