Q: How do you close the icons across the bottom of the home screen?

iOS 7 How to Close Apps

Double Tap the Home Button... Then swipe the App (not the icon) Upwards... Tap the Home Button when finished

From Here  >  http://support.apple.com/kb/HT4211

You close an open app the same way whether it is at the bottom or not.

Double click the home button to see all open apps.  Then swipe up toward the top of the iPhone the icon that appears above the small icons on the bottom row to close any specific open app.