Como inserir uma JPanel de outra classe na principal?

public class Principal extends JFrame implements ActionListener{

   TelaCheque pCheque;
   TelaContas pContas;
   JPanel painelTopo, painelGerente;

public Principal() {
.
painelTopo = new JPanel();
painelGerente = new JPanel();
pCheque = new TelaCheque();
pContas = new TelaContas();
painelGerente.setLayout(new CardLayout());
painelTopo.setLayout(new FlowLayout());
.
painelGerente.add(pCheque,"cheque");
painelGerente.add(pContas,"contas");

getContentPane().add("North",painelTopo);
getContentPane().add("Center",painelGerente);

}
public void actionPerformed(ActionEvent e) {
CardLayout painel = (CardLayout) painelGerente.getLayout();
    if(e.getSource() == miCadCheque){
       painel.show(painelGerente,"cheque");
     	}

     if(e.getSource() == miCadContas){
       painel.show(painelGerente,"contas");
     }

   }

public class TelaCheque extends JPanel implements ActionListener{

  JPanel painelCheque;

public TelaCheque(){

//componentes da tela.

}