Are you having a specific issue? There are lots and lots of tutorials online on how to build and test apps in VS. It depends on the type of app you want to build as to the overall steps. Please refer to the online tutorials for general information. If you have a specific issue or question then we might be better able to guide you from there.
- Get started with C# and ASP.NET Core in Visual Studio
- Create an ASP.NET Core app with Angular in Visual Studio
- Web development with C# ASP.NET Core and Visual Studio
There are many more tutorials available. You can search for the specific type of tutorial you want (e.g. MVC, Razor Pages, Angular, etc).