Hey @Anonymous ,
You would first have to sign out of your samsung account. You can follow these steps:
Settings > Accounts and Back up > Accounts > Samsung account > 3 Dots (Top right corner) > Remove
Once you remove it, you can go ahead and Add account >Samsung Account
That should let you change your email address for your samsung account.
Be sure to click " ✓ Accept as Solution" when you find an answer that works for you.