You can expand the range covered by an existing array formula by following these steps:
  • Select the upmost left cell of the current array
  • Starting from that cell, select a range going downwards and to the right. The range you select must match or exceed the array’s current range both horizontally and vertically
  • With the larger range now selected, click on the formula bar where the array formula should be visible
  • Press CTRL, SHIFT and ENTER simultaneously

After these steps, the array formula should now be filling the larger range you selected.