To create a folder on your iPhone, you need to have at least two apps to put in the folder. When you have decided which apps you want to put in the folder, tap and hold down on the icon of one of them until it starts to shake. As soon as the icon starts to shake, drag it on top of one of the other icons you want to put in the folder.

If you have iOS 4 through 6 the folder that will be automatically created when you drag one app over the other on your iPhone will be a folder with the app names in a strip across the screen. If you have iOS 7 or higher, the folder will take up the entire screen, but you can continue to add more apps to it just by pressing the Home button, then hold down on the next app you want to add until it starts to shake. When that app starts to shake, you can drag it into the folder. You can continue with each icon until you have all the apps you want in any particular folder.

After you have arranged all the apps into a folder that you want on your iPhone, you can edit the folder if you would like to. To do this, tap and hold on the folder until it begins to shake, then tap it one more time and you will see all the contents of the folder at the bottom of your screen. You can then drag more apps into those, or drag them out to remove them from the folder. When you are finished doing this, click the Home button to save the changes. If you want to delete the folder, drag all the apps out of it and then press the Home button.