Take your material and cut it slightly larger than what you're making it for. (your phone/mp3 player/etc.) In this case, I used white felt.
Cut out Hello Kitty's bow, facial features, etc. and then sew them onto one of the pieces you just cut out.
After sewing the face/details on, take the other piece of material and line it up with the other.
Sew the two pieces using a blanket stitch and then you're done! Enjoy your new ipod/phone cozy!