Hello,
DPS 2015 relies on an actual app installed on a device in order to preview the content. You'll need to:
- Set up a Project in the DPS 2015 Dashboard
- Upload content and set up collections
- Generate a Preview app for the Project
- Download and sign the app (this will produce a signed app)
- Install the signed app on your device
That's the short version. Full details are available in the provided documentation.
Hope this helps.