Paint Bucket Tool

Open a design with pattern

Press Ctrl+A to select entire canvas and then press Ctrl+C to copy the pattern

Open another design to give the effect

Click Paint Bucket tool

Select Clipboard Image in Fill option

 Fill in the selected pattern

Pressing Shift and Paint Bucket tool will automatically fill the pattern in all similar colors

              Selected pattern for the design                                                        Selected pattern filled in same color of the design