You can update all your Cotton On & Co. Perks preferences via the Preference Centre at any time, which can be accessed via the link in your emails in the footer here:
If you wish to change your email address that is linked to your Cotton On & Co. Perks account, you will need to create a new account with your new email address and then contact Customer Service via chat clearly stating your new and old email addresses to have these accounts merged.
This ensures all your points and rewards are rolled over. You can contact Customer Service by selecting clicking the help bubble at the bottom right-hand side of the page.