As Bob indicates, it's not clear from your question as to exactly what you mean by 'switch' here.
If, as has Bob has considered to be a possibility, you're referring to changing the email address that you've got registered with AB, click on 'View your profile' and then on 'Edit my profile'. Change the email address shown in both the relevant fields, enter your AB password in the box at the foot of the page and click 'Submit'.
If, though, you mean that you've got a new email account that you want to start using for correspondence and online shopping, etc, you don't really 'switch', as such. You simply stop using your old address and start using your new one. Obviously it would make sense to email everyone in your contacts list, to advise them of your new address. Further, if your new email account offers a 'mail collector' facility (or your old account offers 'mail forwarding'), it would make sense to to use such a facility to ensure that any mail that gets sent to your old address is automatically redirected to your new one. (If you need instructions as to how to do that, please provide the bit after the @ symbol for both accounts and tell us how you access your emails. i.e. do you go to a website or do you use a dedicated email app, such as Windows 10 Mail?)