In the JMRI Preferences . These are the settings for using a Raspberry Pi and a Sprog
System Manufacturer: Sprog DCC
System Connection: Sprog Command Station
In wheezy you have to set this manually Serial Port: /dev/ttyUSB0
In Jessie the location of the SprogII is discovered automatically.
More information for users of outdated version of operating system (Raspian Wheezy supplied with original Model B)