Step 1: What you'll need.
Step 2: Prep your cube.
Step 3: Squares
Step 4: Glue on the squares.
Be very careful not to get any on your hand... its called SUPER GLUE for a reason.
Place the foam cube onto the Rubik's cube. I worked from left to right, top to bottom and found it to be the easiest. Make sure you get the square centered on the first time, the glue dries very rapidly.