My mother is an art teacher and this is how she does this:
You need a piece of cardboard (this will stay on the back of your piece when it is finished), some glue (Elmer’s is fine), the foil and a stylus.
You make the pattern on the cardboard with the glue, so they would trace out their face with glue. When the glue drys, place the foil over the top (you can use a light spray glue to affix it to the cardboard) and press all the areas with the stylus (tracing around the patterns you made with the glue). The glue will form the “embossed” look on the foil. When this step is done, you can take black ink and smear it over your piece. Where there are pits, the ink will remain, but all raised surfaces, the ink will be rubbed off. So this make is look even more embossed.
I hope this makes sense.