Cut the curtain liner so that it is the same size as your curtains. Ignore the curtain loops or the hook area.
Lay the curtains on a flat surface so that the back of the curtains is facing up. Center the insulated liner over the curtains. Fold each edge of the liner back 1 inch to create a smooth edge. This will make the liner smaller than the curtains so the liner is not visible from the inside.
Iron the edges down and pin them in place. Do not pin the liner over the curtain lips or hook area.
Sew the folded edges of the liner to the curtain with a sewing machine. Use thread that matches the curtain so that the stitching is not visible from the inside, or use a contrasting thread color if you want the thread to add a decorative look to the curtain. Do not sew over curtain loops or into the hook area.
Peel the adhesive backing off the magnetic strips. Press the strips on the inside of the bottom of the curtain. Repeat this process with the other three sides of the curtain.
Hang the curtains on the curtain rod.
Peel the adhesive off the other half of the magnets and press them against the wall. Make sure to line them up with the magnets on the curtain.