This article explains how to reorder apps, folders, and basically everything on your iPhone's home screen.
How to Create Folders for Apps on ANY iPhone! [Home Screen]
Reordering apps and folders takes patience, because as you follow the steps below, your iPhone will try to help you out and move icons around. It can be tricky (and annoying) to get it all just right.
To rearrange items on an iPhone's Home screen:
Tap and hold an app until a menu appears. In the menu, tap Edit Home Screen. Now the icons will start to jiggle.