If you would like to password protect certain areas of your website so that only the people with the proper credentials can see that area, you can use the Password Protect Directories tool from your site admin panel.
With this tool, you can protect a single html page or an entire section of your site by moving all the html files for that section into one directory. Once each subsequent users signs up to your page, you can add their username and password using the same tool so that the user name and password is not shared between multiple users.