First: Tap and hold down your finger on the app you want to put into a folder. Hold down on it until the apps start to shake or wiggle. (Click Read More for the rest of the article)
Second: Drag the app across the screen and hold it near the side of the screen until the page turns.
Third: If you let the app go it will be placed on the screen you are on.
Fourth: Press and hold down on the app again and now keep it pressed as you drag it over top of another app.
Fifth: It will now create a folder with both apps included in it. Let go of the app and you should still be seeing the apps wiggling.
Sixth: Press and release the home button and you are done. :)