To change your profile information please add the name details in your Dataiku Profile. You can access the Dataiku Profile also via the link from the Community's and Academy's user menu on the top right of the page when clicking on your avatar image. After you've updated the profile information please sign out from the Academy page and then sign in again to ensure the name information gets updated. Finally when accessing your certificate now from the Academy page it should bear the correct name from your profile.
Please note that if you used the Google or Github account sign in options this option will not be available.