what is the application pool name and adding it

I've been trying to add the application pool to the folders for these sitefinity sites and the application pool names are not found in the local users or groups.
Can someone please post how to find them?
I've been going through the documentation and forum and cannot find it no one's posted these details that I can find so far.
This
www.sitefinity.com/.../configuring-the-iis-to-host-sitefinity-projects.aspx
just says
"You must provide the identity of the application pool,.."
I thought there was a page with a bit more info.

again
thank you

I finally just added IIS_IUSRS
and gave it all the needed permissions.
If anyone knows how to find the specific app pool for a given IIS web site,
please post it.
thanks again