Can you send a screenshot or something to show what you mean? C#, like any programming language, has plenty of buzzwords and it’s not clear what you are asking.
Have you managed to load the test code onto the device prior to you modifying it?
your code should be composed of the following sections:
//these are using statements, they're tangentially related to #include statements in c or import statements in python
//if you use a using statement inside your class rather than the top of the file, it will do something else
namespace TestApp1 //namespaces in c# are logical collections of related classes and structs
internal class Program
static void Main() //Program.Main is the launch point for your program and will execute statements starting here
Debug.WriteLine("This is your error message");