Lay the pocket square flat on a clean surface
Fold it in half to form a rectangle
Fold it again into a smaller rectangle if needed
Adjust the width to match your jacket pocket
Insert the folded square into the pocket
Leave about 1/2 inch to 1 inch visible above the pocket
Smooth the edges so it sits neatly
Straighten the visible top line
Tuck in any excess fabric
Reposition until it looks even and balanced