Access elements bye reference

Need help withthe following:

In the programI createeithergroup orsolo artist.if it'sgroupdo I Group members intoan array.How would Ithen access the members from the veryspecific group?

 case "Gruppmedlem":
                                Console.Clear();
                                Console.WriteLine("\n----------------------------------------");
                                Console.WriteLine("Select Group :");
                                Console.WriteLine("----------------------------------------\n");
                                List<string> groupList = _ml.GetGroup();

                                foreach (string g in groupList)
                                { Console.WriteLine(g); }

                                Console.ReadLine();
                                Console.ReadLine();
                                Console.Write("\nGroup name: ");
                                groupNameAddMember = Console.ReadLine();

                                Group addMember = new Group(groupNameAddMember);
                                Console.Write("Members first name: ");
                                memberFirstName = Console.ReadLine();
                                Console.Write("Membes last name: ");
                                memberLastName = Console.ReadLine();

                                  foreach (byte val2 in Enum.GetValues(typeof(InstrumentType)))
                                  {
                                      Console.WriteLine("Instrument type: {0}:\t{1}",
                                          val2, Enum.GetName(typeof(InstrumentType), val2));
                                  }
                                  instrumentType = Console.ReadLine();

                                  if (!(instrumentType == "1" || instrumentType == "2" || instrumentType == "3"
                                      || instrumentType == "4" || instrumentType == "5"))
                                  {
                                      instrumentType = null;
                                      groupNameAddMember = null;
                                      memberFirstName = null;
                                      memberLastName = null;
                                      Console.Write(myEx.ToString());
                                      Console.ReadLine();
                                      break;
                                  }

                                Console.Write("Instrument: ");
                                instrumentType = Console.ReadLine();

                                Member groupMember = new Member(memberFirstName, memberLastName, program.getInstrumentType(instrumentType));
                                addMember.AddMember(groupMember);   // add a member to the specific group

                                break;

Method should listmembers from a specific Group:

 public List<string> GetMember(string groupName)
        {
            List<string> _groupmember = new List<string>();
            // ????
            return _groupmember;
        }