For 오, just say "Oh" without the w-sound at the end. 어 is like a mix of 오 and 아. Make your mouth round as if you're going to say "Oh" and say "Ah" instead. If you do it correctly you'd pronounce something like the O in "on". As for 에 and 애, check out this video: https://www.youtube.com/watch?v=Ub6QjPkfGHI