The first step I would take to setup a login page would be the database, as a login page needs users to be able to log in and out. The next step would be setting up a register page for users to create a new account, since unless if I created temporary users beforehand, I'd have no means of logging in with users. After registration, I'd send the user to the login page. From here, the user can proceed to login.
To better safe guard my webpages, I would then go over and make sure pages I don't want seen unless the user is logged in just sends the user back to the home page/login page. Furthering this for admin restricted pages also and creating a means to check if a user is an admin.