How to access Objects in Form

Hi

  I have defined below objects in EInvoice class. How i can use these Objects in Form1 and assign value.

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace WindowsFormsApp1
{
    class EInvoice
    {
        public class BuyerDtls
        {
            public string Gstin { get; set; }
            public string LglNm { get; set; }
            public string Pos { get; set; }
            public string Addr1 { get; set; }
            public string Loc { get; set; }
            public int Pin { get; set; }
            public string Stcd { get; set; }
        }

        public class DispDtls
        {
            public string Nm { get; set; }
            public string Addr1 { get; set; }
            public string Loc { get; set; }
            public int Pin { get; set; }
            public string Stcd { get; set; }
        }

        public class DocDtls
        {
            public string Typ { get; set; }
            public string No { get; set; }
            public string Dt { get; set; }
        }

        public class ItemList
        {
            public int ItemNo { get; set; }
            public string SlNo { get; set; }
            public string IsServc { get; set; }
            public string PrdDesc { get; set; }
            public string HsnCd { get; set; }
            public int Qty { get; set; }
            public int FreeQty { get; set; }
            public string Unit { get; set; }
            public int UnitPrice { get; set; }
            public int TotAmt { get; set; }
            public int Discount { get; set; }
            public int PreTaxVal { get; set; }
            public int AssAmt { get; set; }
            public int GstRt { get; set; }
            public int IgstAmt { get; set; }
            public int CgstAmt { get; set; }
            public int SgstAmt { get; set; }
            public int CesRt { get; set; }
            public int CesAmt { get; set; }
            public int CesNonAdvlAmt { get; set; }
            public int StateCesRt { get; set; }
            public int StateCesAmt { get; set; }
            public int StateCesNonAdvlAmt { get; set; }
            public int OthChrg { get; set; }
            public int TotItemVal { get; set; }
        }

        public class Root
        {
            public string Version { get; set; }
            public TranDtls TranDtls { get; set; }
            public DocDtls DocDtls { get; set; }
            public DispDtls SellerDtls { get; set; }
            public BuyerDtls BuyerDtls { get; set; }
            public List ItemList { get; set; }
        }



        
    }
}

Thanks