Fold the aluminum foil along the top line. Cut the excess foil if needed.
Cut the aluminum foil at the corner near the circuit contacts, the contacts must be well separated from the aluminum foil.
Insert the printed circuit foil into the folded aluminum foil and check that the circuit contacts are well insulated from the aluminum foil. The contacts must be far enough from the foil, at least 5 mm or more.
After having checked the contacts extract the circuit foil from the shield again.