Setup
The game engine itself uses .NET Framework 4.8 or .NET Core 3.1 (it multi-targets).
You will need the developer kits for whichever one(s) you will use.
The assets are built using NUKE build. You can set this up in two ways:
Building assets automatically - You will need an extension in your IDE to support NUKE build, (for Visual Studio, it's called NUKE Support), and will need to attach it to the build process (for Visual Studio, you use the Task Runner Explorer).
In Visual Studio, you will need to attach it to the Task Runner Explorer each time Visual Studio starts.
I'm not sure if it's a bug or not, but that's the way it is.
You will need to attach "Clean" to "Clean" and "Compile" to "Before Build".
Manually - If you do not want to do that or cannot do that, you will need to run the _build project every time you want to build assets.
It's a normal C# project, so you would run it like you would any other program.