Thank you for your response.
In the attached screenshot, I covered the account id with a red marker. That is a 10 digit number like 123-456-7890 which is the ad account number. As you can see, the email address associated with that is
onlinesol...@gmail.com, which is the OP of this conversation.
My question is that: how can I change the primary email address to another email address so that this ad account is associated with and managed by the other email address.