how to get private kye for RSA algorithm

using System;
using System.Text;
using System.Windows.Forms;
using System.Security.Cryptography;
using System.Collections;

namespace EncryptionRSA
{
    public partial class Form1 : Form
    {
        private RSACryptoServiceProvider rsaSender;
        private RSACryptoServiceProvider rsaReceiver;
        private string publicKey;
        private string privateKey;

        private int keySize = 1024;

        public Form1()
        {
            InitializeComponent();
            rsaReceiver = new RSACryptoServiceProvider(keySize);
            
            // public key which can be spread to all senders
            publicKey = rsaReceiver.ToXmlString(false);
            // private key. Keep it secret!
            // the private key XML always contains public and private key
            privateKey = rsaReceiver.ToXmlString(true);
        }

        private void textBoxPlain_TextChanged(object sender, EventArgs e)
        {
            // sender using the public key to encrypt data
            rsaSender = new RSACryptoServiceProvider();
            rsaSender.FromXmlString(publicKey);// "loading" public key
            
            // code from your sample
            byte[] bytes = Encoding.UTF32.GetBytes(textBoxPlain.Text);
            int maxLength = keySize/8 - 42;
            int dataLength = bytes.Length;
            int iterationsenc = dataLength / maxLength;
            StringBuilder stringBuilder = new StringBuilder();
            
            for (int i = 0; i <= iterationsenc; i++)
            {
                byte[] tempBytes = new byte[(dataLength - maxLength * i > maxLength) ? maxLength : dataLength - maxLength * i];
                Buffer.BlockCopy(bytes, maxLength * i, tempBytes, 0, tempBytes.Length);
                byte[] encryptedBytes = rsaSender.Encrypt(tempBytes, true);
                Array.Reverse(encryptedBytes);
                stringBuilder.Append(Convert.ToBase64String(encryptedBytes));
            }

            // display encrypted data
            textBoxEncrypted.Text = stringBuilder.ToString();


            // receiver using his privat key
            rsaReceiver = new RSACryptoServiceProvider();
            rsaReceiver.FromXmlString(privateKey);

            // code from your sample
            int base64BlockSize = ((keySize / 8) % 3 != 0) ? (((keySize / 8) / 3) * 4) + 4 : ((keySize / 8) / 3) * 4;
            int iterationsdec = textBoxEncrypted.Text.Length / base64BlockSize;
            ArrayList arrayList = new ArrayList();
            for (int i = 0; i < iterationsdec; i++)
            {
                byte[] encryptedBytes = Convert.FromBase64String(textBoxEncrypted.Text.Substring(base64BlockSize * i, base64BlockSize));
                Array.Reverse(encryptedBytes);
                arrayList.AddRange(rsaReceiver.Decrypt(encryptedBytes, true));
            }

            // display decrypted data
            textBoxDecrypted.Text = Encoding.UTF32.GetString(arrayList.ToArray(Type.GetType("System.Byte")) as byte[]);
        }
    }
}