keep in mind that the smartphones are trying to keep the same aspect ratio and not the screen resolution, so, you'll need to re-size your screen to match the major part of the smartphones on the market.
If you're using HUDs and UIs, you'll need to learn about anchoring your items on the screen, and configuring the parallax setup to match 0.
I still newbie and learning about smartphones too, so, that's what I can share with you for now.