Edit the .htaccess file and add these lines to it:
AuthName "Member's Area Name"
Change the file mode:
chmod 755 .htaccess
Go to this site http://www.kxs.net/support/htaccess_pw.html and generate your encrypted password.
Copy and paste it to .htpasswd file (It's recommended that, you create this file in another directory).
Go to web page, you must give your username and password to enter it!