Hi checks
You just open iis (if 2008R2 - iis would be 7 or 7.5), click websites, click on your website, in right hand pane you will see logs listed. Double click logs and it gives you all information eg log location, what you want to log etc...
You can use php but iis would log by default unless you turn it off and web stats packages gives better human reeadable format but you need to understand certain criteria of how data is derived eg session limits for classing new visits etc...
Many thanks
John