Note: If you reset your homescreen, the first two app pages will revert to the factory layout while the installed apps are on
First pick up your iPhone (or even the iPad) and then open the Settings app. Now scroll down a bit and select the entry "General" from the menu.
At the bottom of the general settings you should now find the menu item "Reset". Touch it now. Reset will find all sorts of useful functions. You can completely erase your device here ("Clear All Content & Settings") or just reset the network settings if problems have arisen. However, to reset your homescreen to factory settings, tap the "Home screen" and then confirm your input again. Your homescreen will now be reset to the factory settings and should now look like a new iPhone.