I open up the bash terminal on macOS and create a new directory for my Web API application. Rather than using Visual Studio, I've been writing all my ASP.NET Core tutorials and examples on my MacBook Pro running macOS and Visual Studio Code. I spend a fair amount of time explaining the details, which my be really useful for you.
If you haven't read my ASP.NET Core MVC from Scratch Tutorial and you are really new to this, I recommend reading that tutorial first. In addition, I will show an example of ASP.NET Core Dependency Injection. I will also build a quick Python Script that uses the Web API. In this article I will create a simple ASP.NET Core Web API Application that allows me to list, add, and remove reminders.