IBM: SCSI Array

Expand raid5 array - IBM X364 class server EXP400 isk chasis

I need to expand a 820gb raid5 array on my IBM X346 server. I have available slots in my EXP400.  What's procedure on how to do this task. Want to add (if I can find new available SCSI drive) U320-3  146.8g  15k  to the other 8 in the box (1 is hot spare)  Software/Hardware used: IBM x346...