Duplicating an object is easy:
  1. Tap on the object that you wish to duplicate.
  2. Find the duplicate button located at the top right of your screen. Tap on this button to begin the duplication process.
  3. After clicking the duplicate button, halos will appear over the selected object. Tap on one of these halos to bring the new object into your game.
You can also duplicate a group of objects, the duplicated group will appear next to the original and will be pre-selected.