You can't enter an Apple symbol directly from the keyboard on the iPhone. There is a workaround that makes it possible to get this character onto the iPhone for use in different apps or as a folder name.
Connect your iPhone to the computer and open iTunes. Make sure your iPhone is selected in the left hand menu and click the Apps tab at the top of the iTunes window. Drag one of your apps on the home screen on top of another to create a new folder. You can also double-click on an existing folder.