Hi Boom, 

Welcome to Box Community!

The steps for adding or modifying your email address are as follows:

1. Login to box.com
2. Go to Account settings (click the profile pic or initials located on the upper right corner)
3. Account 
4. Add a Collaborator or Link Personal Email
5. Link Personal Email > enter the new email 
6. Confirm the new email
7. Go back to account settings and make the secondary email as primary and remove the original email.

I sincerely hope I have provided the support you needed. Thank you for posting!