You're going to have to create some text files, as described in the Wiki article. Notepad, or some other generic WP will work. Just be sure that you save the file as Plain Text.
Find out which version of PHP you're running. This is listed in your Manage Domains-->Edit. Then create the appropriate php-copy.sh file. Put that php-copy.sh file in your home directory (not your website directory). You only need that small script for PHP4 or PHP5, not the "More General Script."
Run those next commands via SSH, then create a .htaccess file with your text editor and put that in your website directory. If your website directory already has a .htaccess, then add the three new lines to the top.
You can use the Panel's new CronTab utility to create that cronjob. Just put the "/home/USERNAME/php-update.sh" in the command field in the Panel and have it run Weekly.