Welcome to 4images forum.
assuming you've installed 4images in /photos/ directory and you are accessing it from your browser at http://yourdomain.com/photos/
try access admin control panel by adding admin in the urle: http://yourdomain.com/photos/admin
if you get 404 error, make sure you've uploaded all files/directories from 4images package, and also referr to docs/installation.txt for additional info about directory structure and permissions.