My problem is related to infragistic installation.

I did an installation and now I have to follow these instructions. The problem is that I don't know a thing about IIS.

First I don't know how to get to IIS. Where do In open it or modify it's parameters?

Please make sure IIS is running on your computer and follow these steps to create the ASP USER:
1) Open .net command prompt

What do I do to open the .net command prompt?

2) iisreset /stop
3) net user ASPNET /delete
4) aspnet_regiis -i
5) iisreset /start

After the .net command prompt is opened I guess that the rest should be easy to do?

Any free help I could get on what is IIS and how it works?