Not using a touch screen and using a laptop for Windows 8 I couldn't work out how to close things like the weather or news apps. Then I thought ALT+F4 the same way you close any software in Windows! It worked.

The other way to close an App in Windows 8 using a mouse is move mouse to the top of the app, left click on it, should turn into a hand, drag the app right to the bottom of the screen and that should close it.