how to add to a list in c#

using System;
using System.Collections.Generic;

namespace add_list
{
        static void Main(string[] args)
        {
            List<string> first = new List<string> { "do", "rey", "me" };
            List<string> second = new List<string> { "fa", "so", "la", "te" };
            first.AddRange(second);
            foreach(var e in first)
            {
                Console.WriteLine(e);

            }
        }
    }
}

List<geo_tag> abc = new List<geo_tag>();
geo_tag tag = new geo_tag();
tag.latitude = 111;
tag.longitude = 122;
tag.unit = "SSS";
abc.Add(tag);