To change resolutions manually go to game client and open LauncherOption.if file with notepad.
Change settings
/DevModeIndex:
//0: 800x600 (4:3)
//1: 1024x768 (4:3)
//2: 1152x900 (4:3)
//3: 1280x720 (16:9)
//4: 1280x800 (16:9)
//5: 1280x920
//6: 1440x900 (16:10)
WindowMode:1 On, or 0 Off