Bahus,
For an open day you don't need to apply online. Bring with your CV and photographs!
Wear business atire. Keep your hair simple and if it's long you should wear it in a ponytail. Make up should be neat and tidy and your nails should be polished. The colour on your make up and nail polish should also be same or at least in the same shade. They also like french manicure.
Arabic is good! Any language apart from English is positive.