How can i avoid repeating a connection string already defined in the appconfig file

I have a connection string in the appconfig file of my c# application  (see below) that writes to a postgresql database.

AppConfig

[]<connectionStrings>
    <add name="Tournaments" connectionString="Host = 138.197.165.89; Database = tournaments; Port = 5432; Username = postgres" />
  </connectionStrings>[/code]

In the method below that goes into my Database  I have had to repeat the string again  (see below)

[] public class PgrConnector : IDataConnection
    {
        private const string db = "tournaments";
        private const string pgrstring = "Host = 138.197.165.89; Database = tournaments; Port = 5432; Username = postgres";
     
        public void ClosePayrollTestRun(MonthPayModel model)
        {
            using (NpgsqlConnection conn = new NpgsqlConnection(pgrstring))
            {

                using (var command = new NpgsqlCommand("public.sppayrollproccesor_closepayrolltestrun", conn))
                {
                    conn.Open();
                    command.CommandType = CommandType.StoredProcedure;

                    //foreach (DataRow row in dataSource.)
                    //{
                    command.Parameters.Add(new NpgsqlParameter("companycodex", NpgsqlTypes.NpgsqlDbType.Varchar) { Direction = ParameterDirection.Input, Value = LoginDetails.staticcompany });
                    command.Parameters.Add(new NpgsqlParameter("mnthyearx", NpgsqlTypes.NpgsqlDbType.Varchar) { Direction = ParameterDirection.Input, Value = LoginDetails.staticmmyyyy });
                    //  command.Parameters.Add(new NpgsqlParameter("staffnox", NpgsqlTypes.NpgsqlDbType.Varchar) { Direction = ParameterDirection.Input, Value = LoginDetails.staticstaffno });
                    // command.Parameters.Add(new NpgsqlParameter("entcodex", NpgsqlTypes.NpgsqlDbType.Varchar) { Direction = ParameterDirection.Input, Value = LoginDetails.staticentcode });
                    string output = "";
                    output = Convert.ToString(command.ExecuteScalar());
                    LoginDetails.staticpayrollproccesorstatus = output;
                    if (output == "-1")
                    {
                        StandardMessages.PayrollScriptError();
                    }
                    return;
                    //}
                }
            }
        }[/code]

I want to avoid the repetition by changing

 using (NpgsqlConnection conn = new NpgsqlConnection(pgrstring))

so that it does not use pgrstring  but the connectionstring coming from my Appconfig file

What would the correct syntax  for the using statement

Thanks

Olukay