its been a while since i setup a scsi squirrel,
you have to have it connected and switched on first,
then switch on your 1200.
insert the scsi setup disc & run,
it should bring up a box with a list of devices,
the scsi squirrel cd is usualy unit 2 or 3 ?
highlight your device, click save.
in devs drawer see if its put in CD0/2/3 ?
if not, in storage copy CD0 to devs/drivers then rename it CD2 OR CD3 ??
click info, in the tooltypes, rename the UNIT=2 or UNIT=3 ?? then double click to mount.
then you need to reboot and it should work.
there is a readme file on the disc.