Hi Suzanne,
You don't need ArcCatalog to copy files to ArcPad - simply copy the entire folder you created during the check-out process onto your field device.
This can be done using ActiveSync for Windows Mobile Devices or by copying the folder between machines using an SD Card or USB Drive.
Once you have copied the folder (called DataForArcPad1 by default) onto your field device, open ArcPad and then use Open Map to browse to the map (.apm) that you created during check-out.
It should be that easy!!
If you have any more problems, please let me know!!
Hannah Ferrier