Start by cutting out two heart shapes out of the red felt.
Cut out of the white felt a rectangular shape with at one end a half circle. Make a little cut in this half circle. Write your (lover's/ pet's/..) name on it, perhaps first with a pencil, then with a marker.
Put the cotton wool between the two layers heart-shaped felt - or you can first stitch the sides of the heart and then stuff it (most probably more logical).
Now it is time to stitch the sides. I like it best when you make a loop and then put your needle through it. Stitch the little flap of the half circle between the two layers red felt. You only need a few stitches to secure the white felt to the heart.
Pierce a safety pin in the back layer or attache a bobby pin to it.