The most basic answer would be that 이에요/예요 is when you are saying "that is/this is ______." You are stating what something is. 첵이에요 this is a book/ it's a book 선물이에요 this is a present/ it's a present 고양이예요 it's a cat 뭐예요? what is that? 있어요 is when something exists. So questions like "do you have/i have _____" or "is there/there is _____" 강아지 있어요(?) i have a dog/ do you have a dog? 어디 있어요(?) where are you/ where is it 커피 있어요 there is coffee/ do you have coffee? etc etc if you need more help or information you can look at lessons from Talk to Me in Korean 이에요/예요 http://www.talktomeinkorean.com/lessons/l1l5/ 있어요/없어요 http://www.talktomeinkorean.com/lessons/l1l10/ i hope that helps!

The way I think of it is that 이다 (이에요/예요) is the verb of "equality" (this is a bird, that is a book). And 있다 (있어요) is the very of "existence". (I have a book, there is a need = a need exists). Hope that helps rather than confuses. ;)