You could probably start with whatever point of contact from your back you can, just putting your back against the wall and practicing the motion until you can eventually rest other parts of your back. This is a very proprioceptive exercise that involves the shifting, strengthening and stretching of muscle fibers, and it's not easy at all even for people without scoliosis, so don't get frustrated if you don't see immediate results. Given that you have scoliosis, even if you don't see any results at all for months I wouldn't be discouraged, since you're starting off from a different point than other people. Obviously I'm just a random internet person and not a licensed physician, so take everything with a grain of salt and stop if you feel any sort of pain since you could be compressing a disc. What works for me is to try to rest my lower back on the wall, even if the upper back remains somewhat slouched and detached from it, bracing my core and doing the raises. If performed properly, I feel my upper back, neck and shoulders start to align backwards. My ex had spinal fusion and found this exercise helpful. Best of luck.