first you have to add your panel to your layoutmangager.
sth like
add(p0);
and then you need a call to pack of the JFrame
pack();
if you want 2 panels, you have give them a position in your frame / layout manager.
f.add(pane1, BorderLayout.WEST);
f.add(pane2, BorderLayout.EAST);
you have 3 possibilites to set the size on your components:
setPreferredSize(Dimension D);
setMinimumSize(Dimension D);
setMaximumSize(Dimension D);