typically it will reside in one side, as a semi-hidden like-tab thing,
tapping on it with the pen will open the panel

once you press insert, the normal behavior its that it will hide again to
the same place

there are however more ways to make it appear, in the taskbar you can put a
button to call the input panel (right click on taskbar / toolbars / tablet
pc input panel), if you are really working in a tablet pc (not sure about
"normal" pcs with a digitizer) when you click on a text input field it will
appear a little icon near it to call the input panel, a third method would
be configure the input panel to open with its own gesture