Example of creating a custom section in Umbraco

installer.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Net;
using System.Xml;
using Umbraco.Core;
using Umbraco.Core.Models;
using Umbraco.Core.Persistence;
using Umbraco.Web;

namespace ExamplePackage
{
    public class installer : ApplicationEventHandler
    {
        protected const string ExampleSectionAlias = "example";

        protected override void ApplicationStarted(UmbracoApplicationBase umbracoApplication, ApplicationContext applicationContext)
        {
            // Gets a reference to the section if the section is already added
            Section section = applicationContext.Services.SectionService.GetByAlias(ExampleSectionAlias);
            if (section != null) return;

            //Add a custom Section
            applicationContext.Services.SectionService.MakeNew("Example", ExampleSectionAlias, "icon-smiley");
        }
    }
}