Once you have expresspcb setup, it should create these directory structures for you:
C:\Users\Owner\Documents\ExpressPCB\SchComponents_Custom
You can then paste these 2 files in to have a headstart on arduino based schematics
http://www.crossroadsfencing.com/Arduino Mini-Pro.s
http://www.crossroadsfencing.com/Generic 328 Arduino.s
I've not actually tried that, so it may or may not work.
The directory does just seem to list all the symbols I have created tho.