Question about the position of frames on my face!

[cheap glasses]

Here is my simple question before the optician start my eyeglasses, though this is not my first time to buy eye wears, I haven’t figure our this question for a long time, I just what to know the position of the glasses on my face, I get used to wear eyeglasses at top of nose, did I put down the right position? What does it mean wearing it on the forehead? Buy the way, plastic frames don’t have special nose pads, do I need to put them at the same position as metal ones?