Have your Ipaq with Navman sleeve attached, switched on and connected to your PC in it's cradle...
Run PocketFMS on your PC and set it up with the flight plan / maps etc that you are going to use, then Click the "Synchronise CE Device button" on the top row ( 9 buttons from the left - icon has 2 small computer screens and a red connecting line between them.
This should then send the program, all the info and maps to your Ipaq.
You should then be able to start PocketFMS on your Ipaq - it will be in Start / Programs and you should also have an Icon to click on at the top of the Start Menu which looks like a Compass Rose.
Once you have started the program you may have to manually select the GPS device settings from the opening screen - your Ipaq with Navman will probably be "GPS On COM4" and 57600 Baud - if these aren't detected from the default Auto detect settings then you can change them manually.
Click on "Enable GPS" and make sure you are somewhere that the unit can "see" the satellites ( I found it didn't work too well from my Lounge ! )
Click the "Menu" button ( Bottom Left ) click the "Page" button ( Top right ) then the "Moving Map" button - once your Navman has locked on to the satellites your map should be displayed.
There are loads more instructions including how the program reconfigures the various Ipaq buttons for quick access - all this can be found on the help file which is included with program when you download it or it can be downloaded as a stand alone file here :
PocketFMS Help File
Have fun :-)