Hey FlameX.
What you are doing is creating what is called an "intranet" instead of "internet". An intranet is a local grouping of nodes and web sites to be used internally only and not shared with the internet.
In response to your question I have googled a link for you
here.
I also suggest doing some google searches using keywords "intranet", "IIS", "intranet website" and so on. There is a great wealth of information online that will help you get started. As far as setting up the IIS server itself, it is a very simple task and it installs very much like any other software. Configuring the IIS server may seem complicated however for your needs the default setup with minimal tweaking should be sufficient.