QStringList  header;
header << "Number" << "Indonesian";

ui->QTableWidget->setHorizontalHeaderLabels(header);

for (int i = 0; i < header.length(); i++) {
      QFont font = ui->tableWidget->horizontalHeaderItem(i)->font();
      font.setBold(true);
      ui->tableWidget->horizontalHeaderItem(i)->setFont(font);
}