It should look like this. Check what works for your elf. Stick it.
After that, make small tears and stick them to the front of the hat, in the forehead. They will be the hair.
As you can see on the image, I added some dots under the eyes. You can make them with an edible marker or with a brush and your favourite colouring. But, they are optional. You can also blush the cheeks with powder colouring and a brush.