From the step where you enter your design's size:

1. Enter the size for the individual copies. (Not the overall repeated size.)
2. Click the Repeat button. It's below the Print button.
3. In the Repeat tool, you can set how many copies horizontally & vertically and their spacing.
4. When done, it takes you to the resizing step with the repeated design. There you can print it.

If you want to only reflect a quarter or half design, you can use the Reflect tool. From the page where you enter your design's size, first click Customize then Reflect.