Hi,
It's actually not the easiest thing, but to see all open apps, just first have an app running on screen. You can't do this from the home launcher screen. At the very bottom of the running app is a bar. Put your finger at or just below that and drag slowly up until the app reduces and is dragged up. Then let go of the bottom button. You can now scroll through open apps. To close any, just swipe it right. To close all, scroll quickly to the very bottom of the open apps list for the "Close All" button.