Custom oscommerce 2.3.1 first page

I want the first page you land on of my oscommerce 2.3.1 store to just be a login box for usename and password and forgotten pass link etc with nothing else, so the users have to log in to view the catalog, if they try to navigate to a page without being logged in it will just redirect them to the login box. You will need to have an install of oscommerce 2.3.1 to test it on I will require a text file with what changes I have to make and the steps to do it and any files if required. Thanks