Help With Mobile Game

For the past few weeks I have been using GDevelop. And I really like it. A few days ago I was testing to see if my app would work on my phone. And It kinda worked. The app worked fine, no problems there. But I had issues with screen resolution. Here is a screenshot to show you what I mean:

As you can see the app works. But it doesn’t look correct.
First. I don’t know how to get the app into fullscreen. (This would probably fix the white boarders, because for the screen resolution I put in my phones resolution). I would really appreciate it if you could tell me where I can enable fullscreen (In guessing it is somewhere in the Intel XDK. But I’m not 100% sure.