sorry i was writing a reply and my phone decided to delete it
basically you can choose to get glasses that will complement your face shape like so:
or you can decide to emphasise your features by getting frames in the same shape as your face, like jean pierre coffe (round face/round glasses)
imo the most important is that your eyes are in the centre of the glasses, your eyebrows just above the frames and the frames should be as wide as your face.
try on lots of glasses and you will get an idea of what suits you. bringing a friend also helps.