Well just looking at the picture is pretty self explanatory. Just cut out two identical ghost shaped pieces of white felt.
Then add the eyes with black thread on one piece. Be creative with this part. You can use buttons and even make a mouth.
Then sew the two pieces together. (wrong sides facing each other) Leave a small space to stuff.
Add stuffing and finish sewing! You can pretty much do anything with felt. Have fun. Happy Halloween!