Despite being planned to go up as soon as the Sony conference ended there is no sign as of yet of the Resident Evil 7 demo on PS4. The demo is exclusive to PS4 users only with PlayStation Plus and will be able to download soon.
To download the demo, open the PS4 store, and then go to games, the demos. The Resident Evil VII demo should be there to download very soon.
UPDATE: The demo is live! Check out the news here
Resident Evil 7 releases in January 2017 for PS4, Xbox One, and PC.