If your screen is set to 1366×768 then Traktor should be able to just use that.
Don’t forget to enable full screen mode. If Traktor is running in a window, then click on the button with the square, in the top right, right next to the “NI” logo. That should set Traktor to full screen mode. You can also configure Traktor to start up in full screen mode, in “Preferences” -> “Global Settings” -> “Miscellaneous” -> “Switch to Fullscreen on Startup”.
