This article explains how to change your primary email address on the Facebook website and mobile app, and how to delete an email address from your Facebook account.
How to Change Your Email Address on Facebook – Complete Guide
You can change the email addresses associated with your Facebook account from any computer, whether it's a Mac, Windows, or Linux computer, by using your favorite web browser.
To change your primary email address on Facebook:
Log into your Facebook account and select the down arrow in the top right corner.