I'm very new to this, I followed the directions to a tee. Is the last step for 1.5.x versions to go setup a Cron job via the control panel?

I'm having issues on how exactly this is done, it's not really told the details on how to do this.

In the admin there's an option to 'view, truncate or delete', should I be 'truncating' the different xml files? what does that do?

thanks for any help