Closing a program or app in windows 8 is little tricky. There is no direct [X] button located in top right corner of apps / program windows to close that app.
Windows 8 is highly optimized to use less memory / RAM and CPU. Any inactive program / app is automatically suspended by windows 8 and thus save lot’s of system resources. You do not actually need to close any app / program because windows 8 will automatically suspend all inactive apps.
When you open a new app or switch to a new app, the system will automatically send old app to suspended state after 5 seconds.
In this way windows 8 save lots of system resources and make windows 8 lots faster and smoother.
Technically you do not need to close apps in windows 8. But if you still want to close running apps for some reason, you can close it from Windows Task Manager. Press SHIFT + CTRL + ESC button to start task manager and then you can close the apps. Select the app and press End Task button.