You need to buy Photoshop Touch separately via iTunes.
Hope that answers your question.
Adding to what Guido said, PS Touch is in several closed electronic marketplaces (Google Play, iTunes & Amazon's Appstore) so there's no easy way of linking those to your CC account.
That being said, once you buy PS Touch, you're practically locked in for any updates. (And PS Touch has come a long way since version 1.0.)