Update values from one column in same table

Question

 

THis Is My Code Please Edite This Code 

if (msf.Text != "")
{
cmd = new SqlCommand("insert into tbl_sinking(CHARG) values(@charg)", sqlcon);
sqlcon.Open();
cmd.Parameters.AddWithValue("@charg", msf.Text);
cmd.ExecuteNonQuery();
sqlcon.Close();
MessageBox.Show("Record Inserted Successfully");
DisplayData();
ClearData();
}
else
{
MessageBox.Show("Please Provide Details!");
}