How to close running apps in windows phone 8?

[Jim]

Hello,
I would like to close my twitter app on my Lumia 920, but when I hold down the back button for multitasking, I can't figure out how to close an app. Does anyone know how?
Thanks!

[Spieler]

keep on pressing on the back button
till you open the multitasking then after that press on the twitter app
when its open keep on pressing the back button
and that way you will go back to your start screen
and you will close the app
hope i helped
if you need any more help or got a question you can email me at spieleranswers@outlook.com
and btw the lumia 920 is an amazing phone are you happy with it?