This plugin is pretty simple. Though for a PHP4 driven site, currently only FTP archiving is available. It is highly recommended that to get the most out of this plugin & to enable the best data protection; you use an FTP account that is truly remote, meaning separate domain name (and more importantly, separate a IP address).

It's a good idea to store the following two items on your own, (in the same place as wpTimeMachine-archive, which is the archive file generated by the plugin).
Your copy of WordPress:
Your copy of wp-config.php For security purposes this file is not backed up!

Here's some relevant information to post to the WordPress forum, if you need help: