Problem with PADLEFT

Hi everyone , first thank you for reading this, I'm very rookie to develop in C#, and I'm trying to develop an app for university (just for practice), well it's not finished yet, But I have a Problem with the "Padleft", take a look please I need Help. Sorry for the code I'm really very rookie here you are.
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  namespace Payment
 {
 class Program
 {
 public struct University
 {
 public string StudentName;
 public DateTime InscriptionDate;
 public DateTime EndDate;
 public decimal Payment;
 //public string Signatures;
 public int StudentID;
 
 
 }
 public static void Main(string[] args)
 {
 
 
 
 int TotalData = 5;
 int Capacity = 0;
 University[] Regedit = new University[TotalData];
 
 
 
 string PleaseSelect;
 
 Console.WriteLine("Wellcome to the university!:");
 Console.WriteLine();
 Console.Write("\nSelect the option:");
 Console.WriteLine("\n1-Create a new student:");
 Console.WriteLine("2-Search for Student payment");
 Console.WriteLine("3-No paid");
 
 
 PleaseSelect = Console.ReadLine();
 switch (PleaseSelect) 
 {
 case "1":
 if (Capacity < TotalData) 
 {
 Console.WriteLine("First data:", Capacity + 1);
 Console.WriteLine("Write the name of the student please!");
 Regedit[Capacity].StudentName = Console.ReadLine();
 
 Console.WriteLine("Student' ID");
 Regedit[Capacity].StudentID = Convert.ToInt32(Console.ReadLine());
 
 /*Console.WriteLine("Selection of signatures");
 Regedit[Capacity].Signatures = Console.WriteLine();*/
 
 string[] Signatures = new string[5];
 string Selections;
 int i;
 for (i = 0; i<= 4 ; i++)
 {
 Console.WriteLine("Start your selection:{0}",i+1);
 Signatures[i] = Console.ReadLine();
 }
 
 Selections = string.Empty;
 for (i = 0; i <= 4; i++)
 Selections += Signatures[i];
 Console.WriteLine("Your selection:{0}",Selections.PadLeft(Signatures[i]));
 
 
 
 Console.WriteLine("Payment");
 Regedit[Capacity].Payment = Convert.ToDecimal(Console.ReadLine());
 if (Regedit[Capacity].Payment != 50) {
 Console.WriteLine("No Enough for the quarter");
 }
 else Console.WriteLine("You payment is good have a good luck!:");
 }
 
 break;
 default:
 
 break;
 }
 
 Console.Write("Press any key to continue . . . ");
 Console.ReadKey(true);
 }
 }
 }