can someone pliz help me understand what this challenge wants coz um now stck

using System.Web.Mvc;
using IssueReporter.Data;
using IssueReporter.Models;

namespace IssueReporter.Controllers
{
    public class IssuesController : Controller
    {
        private IssuesRepository _issuesRepository;

        public IssuesController()
        {
            _issuesRepository = new IssuesRepository();
        }

        public ActionResult Index()
        {
            return View();
        }

        public ActionResult Report()
        {
            var issue = new Issue();

            SetupDepartmentsSelectListItems();

            return View(issue);
        }

        [HttpPost]
        public ActionResult Report(Issue issue)
        {
            if (issue.Severity == Issue.SeverityLevel.Critical && string.IsNullOrEmpty(issue.Email))
            {
                // TODO Use the ModelState.AddModelError method to add an error message for the "Email" field.
            }

            if (ModelState.IsValid)
            {
                _issuesRepository.AddIssue(issue);

                return RedirectToAction("Index");
            }

            SetupDepartmentsSelectListItems();

            return View(issue);
        }

        private void SetupDepartmentsSelectListItems()
        {
            ViewBag.DepartmentsSelectListItems = new SelectList(
                Data.Data.Departments, "Id", "Name");
        }
    }
}