If you have got a new email address and you want to associate this email address with your Facebook account, then you can change the email address in Facebook account using the Account Settings option. This is similar to changing the password of a Facebook account.
Click the Account dropdown arrow and select Account Settings from the menu list
Under the settings tab, navigate to the Email section and click the Change link.
The Email section will expand with the following option for specifying the new email address.
Enter the new email address in the New Contact Email text box and click the Add New Email button. By this way a Facebook user can change his contact email address.