To get your definitive path or absolute server path, upload this in a file called path.php into the directory you're looking to protect...
<?php
echo getcwd();
?>
Then view it in your browser by going to it such as yoursite.example.com/path.php... it should display something like /home/vol#/example.com/user_123456/htdocs/path.php and everything before the path.php bit is your path.
From there use the following format for your .htaccess adjusting where necessary...
AuthUserFile /home/vol#/example.com/user_123456/htdocs/.htpasswd
AuthGroupFile /dev/null
AuthName "Private Area"
AuthType Basic
<Limit GET POST>
require valid-user
</Limit>
Then upload .htpasswd into your HTDOCS folder using a format similar to this in which the username is
chicken and the password is
cheese which is encoded using the encoder linked here:
http://home.flash.net/cgi-bin/pw.plchicken:XixxrFOdloHMc
For each user simply add a new entry below the previous one.