You can change your email address in the settings panel in the top right corner by clicking My account -> My profile, and then selecting "Change your email address".

After changing your email, you will receive a confirmation link to your new address - you must click it to activate your new email.

Until the new address is confirmed, the old address will be active.

If you have logged in to Mafelo using a Facebook account associated with the old email address, then you will no longer be able to log in with it. If you logged back in using FB, a new blank account would be created with your old email address.