To sync an existing Fotolia account with a new Adobe Stock Contributor account visit contributor.stock.adobe.com
If you are using the same email address for your Adobe ID that your Fotolia account is set up with then the process to sync will be automatically triggered.
If your email is different then you must answer "yes" to the question "Are you an existing Fotolia contributor?" Once you click yes, you will be prompted to enter your Fotolia credentials and the sync will be complete.
"Note: Syncing your Fotolia account is only possible the first time you log in to the Adobe Stock Contributor portal."
Wish there was a way to do this if I missed the 'one time only' option first time I logged in.
Contact support and ask to get transfered.