If you have a gmail address in your profile, or an address in the "Other email address" field, you can have a password-reset message sent to either of those addresses. Simply click "Forgot your password?" on the login page and enter one of the addresses in your profile.
If you have forgotten your password, no longer have access to the primary email address associated with your account, and have no other address in your profile, then you need to supply evidence that your new email address belongs to you. That is, you need to supply evidence that your new address and the one currently in your profile belong to the same person. One way to do so is to supply the following URLs.
The URL of a page on the official website of your current institution that lists your name, position, and email address.
The URL of a page on the official website of your current institution that has a link to your cv, showing your previous and current affiliations.
The URL of a published paper or other document that shows the email address currently in your profile.
Alternatively, if you have an applicant account with a photo in it and you can give us the URL of a page on the official website of your current institution
that has a photo and your current email address, we may be able to use that to verify your identity. (Please note that a photo on a personal website, which you control, is not