Now that you have created the Visualforce page you need to make sure that your Salesforce users have permission to access it.
Edit Page Permissions
Add any necessary profiles to the list of Enabled Profiles. Any user with a matching profile will be able to access the login page. If the user does not belong to a profile listed under Enabled Profiles then they will be presented with an error stating that they don't have permission to view the page.
Remember that if you are doing this in a sandbox org you will also need to update permissions in your production org.