If you have more than one Adobe ID and would like to change the Adobe ID that you use to login to Behance, you can do this from Account Settings under Switch Adobe ID: https://www.behance.net/account/settings
Some may choose to do this in case they have an Adobe ID that has paid products associated with it. For example, if you are a Creative Cloud subscriber, Adobe Portfolio comes free with your subscription, so you may want to associate your Behance account with that Adobe ID. Once you link to a new Adobe ID, that will be your new login email address.
NOTE: If you also have a connected Adobe Portfolio, you will see a different pop-up; please contact us here for the support code.