The quickstarts provide step by step instructions for various common Duende IdentityServer scenarios. They start with the absolute basics and become more complex - it is recommended you do them in order.
Every quickstart has a reference solution - you can find the code in the samples folder.
The first thing you should do is install our templates:
dotnet new install Duende.IdentityServer.Templates
They will be used as a starting point for the various tutorials.