The same goes for your email address verification process, the payment verification email will be auto-triggered to you upon adding it. If you have not received the email, please check your spam or junk mail folder (yes, this may sounds cliche, but most time it does the magic!).
You may also try to save firstname.lastname@example.org to your address book to see if you can find the confirmation email. Shopback takes customers' payment security seriously, thus, kindly ensure you pass this stage with flying colors ;)