iFixit

On the keyboard, remove the F1, F2, F11, and F12 keys.

This is scary - take a deep breath before continuing. Place your index finger under the upper left corner of the key and lift up until you hear a click. Then, transfer your finger to the left edge of the key and lift up to pull the key off.

You're freeing the two tabs on the left of the key from the two small holes in the plastic scissors mechanism.

When replacing the keys in the keyboard, place the key directly over the slot where it will go and press down until you hear the key click into place.

Use your fingernail or a small flathead screwdriver to peel up the gray stickers covering each of the screws.