Secure Communications

I have a win std 2003 Windows server running iis 6.0
I am trying to publish a cerrificate for a website
however when i goto
iis>(server)>default website>properties>directory security
the area "Secure Communications" is grayed out
the help says

Windows provides means to secure communication between the client and the
Web server using server certificates and certificate mapping. You can
implement secure communications by enabling Windows directory service
mapping, which allows you to use the Directory Service client-certificate
mapping rather than one-to-one or many-to-one mapping. To enable this
service, the server must be a member of the Windows® Server 2003 domain.

I can't find much info on Windows directory service mapping but what i can
find says to make sure
iis>(server)>default website>properties>directory security
secume communications>
enable the windows directory serive mapper is checked
it is...

any idea on how to ungrayout this?

thanks
Steadman