Go to your account settings by clicking that little gear at the top right hand corner of the Facebook page. Go to the "general" tab on the left side of the screen and that will take you to the General Account Settings page, but usually when you click account settings, it automatically takes you to that page anyway. You'll see a list starting with Name, then Username, and Email right under that. At the end of the row that says Email, there will be the words "Edit" and a little pencil looking logo next to it. Click on that and you should be able to change it from there. Hope this helps.