Press and hold any icon on the Home screen until they all start to jiggle. Now touch and hold an app or bookmark that you want to put into a folder with another app or bookmark. Without releasing the icon that you're touching slide it across the screen until it's over the other app/bookmark etc that you want in the folder. Release the icon and the two will form a folder with both apps/bookmarks etc inside. Continue that process merging apps etc into folders. If you subsequently briefly touch a jiggling folder, you'll be offered the option to give it a suitable name. By default, the iPad names the folder after the app that formed the folder initially. Once you've finished making folders, press the Home button to stop the icons/folders jiggling.
Tim