"no" vs "em"

[Koreatown]

How to know when to use which one?

When I translate the sentence, "I want breakfast in my room," my first instinct is to say, "Eu quero café da manhã em meu quarto" but according to the lesson it's actually "Eu quero café da manhã no meu quarto."

Same for "Tem leite na geladeira" - is "Tem leite em a geladeira" incorrect?

[Paulenrique]

Everytime we have em + article we have to link (no, na, nos, nas). Sometimes its opitional to use the definite article before possessives. If u use, you have to link. Its incorrect to say "tem leite em a geladeira", you have to use na (em + a). As for "no/em meu quarto" you can use both since u choose to use the article or not.

[Koreatown]

Thank you for the clarification. It makes a lot more sense now

[Paulenrique]

further information on when using definite article before possessives: http://duolingo.com/#/comment/64947