How to find what we want on Quran?

I am non-Islam, but I like to learn Islam. But I don't know that how to search something on Quran. Eg: I read https://islam.stackexchange.com/questions/312/is-a-woman-required-to-have-sex-with-her-husband-whenever-he-requests-it . Most upvoted answer stared as "Yes that's true.". So I want to find on Quran where it was mentioned?