Documentation for adding disk unit

Can anyone tell me where I can find some documentation on installing a
new disk unit to a RAID set? I've looked at the InfoCenter, but I must
be missing something. I'm trying to add a new disk unit and I've never
done it before. So far I've put the new disk into the expansion slot and
I can see the un-configured disk when I'm working with disk
configuration in system tools. I think I need to include the unit in the
device parity before I can add it to the ASP, but I don't know for sure.
Can anyone tell me if this is true? Also is this something I should be
doing during off hours? I'll keep searching for instructions. 

Thanks,

Griz