VS Code is a fairly lightweight and bare-bones IDE. You'll need to install C# to get started. When you launched VS Code for the first time, your browser should have opened to the Getting Started page on the VS Code website. If it didn't, go there now (https://code.visualstudio.com/docs).

There are a variety of useful extensions that you can install from the marketplace. For now, all you will need is C#. At the time of writing, C# was listed near the top of the Top Extensions list. Click on the C# tile (or find it by searching in the marketplace) to learn more about this extension.

You should see that the installation instructions direct you to launch VS Code Quick Open (Ctrl-P) and paste the following command:

ext install csharp

From within VS Code, paste the command into the Quick Open section and press Enter. Find the C# version powered by OmniSharp and choose Install. Once the C# extension is installed, you will need to reload VS Code to activate the C# extension (choose reload).