All Class Central profiles are private when created, but you can make yours public so others can see your profile, including the courses you have finished, your public Lists, and all the reviews you have written.
To choose between Private and Public, go to Your Profile (in the drop-down list when you hover over your image at the top right), then Edit Profile. Select the Public/Private toggle under Profile Visibility, then select the Save button.
Reviews you have added while signed in to your Class Central account display your username and profile picture, whether or not your profile is public. Reviews added when not signed in are marked Anonymous.