To load soundbank into the A station, you'll first need the following software:
If you are on a PC, you'll need MIDI OX (http://www.midiox.com/)
If you are on a Mac, you'll need SysEx Libraian (http://www.snoize.com/SysExLibrarian/)
Load the sound into the software, and send it to the A-station via a midi interface.
Once the soundbank are sent, it'll only be save to the A-station's RAM, so to save it permanently, first you need to check if memory protect is on or off. To do this go to 'Utility' mode, and check if the LED on the left (labelled porta/data) is on. If it is off, press the 'Unprotect/+' button to unprotect it. Next go to 'Save' mode, make sure the LED light is on (which indicate memory is off), then press 'Write/+' to save a sound.