C# OO - DLL Files - How to Create .dll

DirectPrinter.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace DirectPrinter
{
    public class DirectA
    {
        public static void DirectPrintA()
        {
            Console.WriteLine("Line from DirectPrintA Method, from DirectA Class");
        }
    }
    public class DirectB
    {
        public static void DirectPrintB()
        {
            Console.WriteLine("Line from DirectPrintB Method, from DirectB Class");
        }
    }
}

Program.cs

using System;
using DirectPrinter;
//using DDPA = DirectPrinter;

namespace LearnCS
{
    class Program
    {
        static void Main(string[] args)
        {
            Console.WriteLine("I am from Main File");

            ExternalSource.ExternalMethod();
            Console.WriteLine("Variable from External Source: " + ExternalSource.x);

            //Stuff from External Source

            DirectA.DirectPrintA();
            DirectB.DirectPrintB();

            Console.ReadLine();
        }
    }
    class ExternalSource
    {
        public static void ExternalMethod()
        {
            Console.WriteLine("But, I am from External Method");
        }

        public static int x = 100;
    }
}