One could start by screaming and tearing one's hair out in chunks. It would probably be less painful and far, far less annoying and frustrating. The reason? BT, with whom I have dealt for longer than I care to remember, despite a range of hassles and problems over the years, has notified me that, unless I pay them to keep my email addresses, these will cease to function next month.
I have, as a result managed to create a new email for myself with Google Mail, which is fine, but which comes with the problem that I cannot now change the email for this Blog to a 'gmail' address! Why? Who knows, getting in touch with anyone at Google or Blogger to find out is like ... well, let's put it this way, I could probably get to Mars with less difficulty. So, now I'm stuck with a Blogger Account that won't let me change my email, and won't allow me to change the primary email account on it to my new 'gmail' address - even though Blogger is a part of the Google empire.
To make life even more entertaining, I have now tried every trick I can think of (and a few suggested by computer gurus) to get my address book from the old BT account, transferred to my 'gmail' account. Don't be silly, it ain't happening. The BT system says I can move it to Yahoo. Tried that, didn't work. It also says I can move it to Microslosh Outlook. Don't want to do that even if I had Outlook, because I use a Mac.
So, it looks like I'm going to have to go back to basics, and find a way to print out the entire BT email address book, then manually re-enter the addresses I want into my new mail account. If anyone can tell me how to resolve all the other issues, like changing my email address with PayPal, various things I subscribe to, Blogger and the hundred and one things I seem to have a "registered email address" for - please let me know in the Comments - email seems to be a problem at present!