Enter the e-mail address you supplied when you created the account. Information about all accounts registered with this e-mail will be sent to that address.
You only need to log in if you want to submit data or update existing submissions. Browsing or downloading GEO's public holdings is unrestricted and does not require an account.
IMPORTANT: After logging in to My NCBI you will be given the option to link that account with your legacy GEO account and thereby gain access to existing submissions.