AUTHORIZATION With WINDOWS AUTHENTICATION -- HELP!!

i want to implement authorization with windows authentication and don't
have the slightest clue of how to do this implementation. the basic
windows authentication for this .NET application is already setup. my
problem lies within my inability to manipulate the username captured in
the authentication process and my knowledge of how IIS is involved.

specifically, i have the following questions:
1) what object(s) can be used so that the user's username can be
manipulated for the authorization process?
2) in order to apply roles, do the users need to be placed in groups in
IIS? if so, how does this work?
3) is all the code that the application uses for roles in web.config?
or does global.asax play a role in this matter?
4) does the web.config file know to communicate with IIS because the
authorization type is set to windows?
5) once authorization is in place, can a section of an .aspx file be
visible to a group or can only entire files be secured for a group?

as you can see, i'm trying to figure out the relationship between
authorization and windows authentication so any help would be
appreciated.

thanks,
john
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