If it's just a few users you want to give access to you site using MySQL is overkill. You're probably better off doing this using .htaccess and .htpasswd files.
Just add these two files to your site. You can create .htaccess (don't forget the dot in the name!) using a text editor. Its contents should be something like this:
AuthName "Password protected site"
Put the file in the directory that you want to protect.
The other one, .htpasswd, contains the passwords for the users that are allowed access to the site.
You can create it with the follwoing command:
htpasswd -c .htpasswd your-user-name
where your-user-name is the login name of the user you want to give access. You will have to enter a password for that user. The htpasswd utility creates a file called .htpasswd in your current directory. Just move it to the directory you want to protect (like the .htaccess file).
If you want more info on this just search for .htaccess on google. That should give you plenty of useful links.
Hope this helps,