i can't drag my app icons on the home screen

Did you tap and hold down on an app icon until they al "wiggle"? That is how you move icons around on the screen or create folders by dragging one app on top of another. Then you tap the home button when you are done.

If the icons are wiggling and some are showing an X then you should be able to move them. While they are wiggling Tap and hold on an icon until it grows slightly then slide your finger to a new location. You cannot move an icon lower than the end of the last row on a screen. Moving it to the edge of a screen will move it to the next screen.

You can move icons off of and on to the dock at the bottom of the screen as well.

Note: Tapping on an X while an icon is wiggling will delete that app.

What about if the app icons are not on the home screen? After the iOS 7 update, all of my home screen app icons are gone. If I double tap the home button, I can see all of them in a line at the bottom of the screen, how do I drag them back up to the home screen?