Make sure to do the trial with a normal registered user to upload an profile image, and not a moderator or an administrator, those are not moderated.
You can also try on our demo site (link in top menu), as I just did now:
1. Login as normal Demo User
2. Click on "DU" icon or avatar
3. Click on "Edit" "Update your profile"
4, In Portrait, upload a new image
5. See it doesn't yet display.
6. Logout
7. Login as moderator, go to Demo User profile, you will see the "Approve" and "Reject" buttons.
On demo site, to see the CB Workflows module, you need to create it as it's not created by default and pubish it in "sidebar-a" position. Then you will see it on the front as administrator on the top left displaying "1 image approval" link, allowing to review and approve the images.