your post is confusing.
you say it worked fine, but then it sounds like your upset it doesn't have audio.
what mac do you have?
how to hook it up depends on what kind, and how old it is.
if you're not sure how old it is, go to the

menu, about this mac, more info.
then on the the main hardware page, there is a Model Identifier should say something followed by a couple numbers, like "Macmini4,1"
give us that, and we can tell you what you need.