Just go to intel SDK and open your project setting. Scroll down to "Build Settings" select "Croswalk" and mark the fullscreen checkbox. Your next build is going to be fullscreen. Fullscreen in this case means a hidden status and navigation bar that you can swipe in to see.
If you are talking about the emulator instead of a build that is somehow not working on start. Just mark the box on the right 'show status bar" and deselect it again. Your emulation should be updated on air in fullscreen mode.