If you mean Google voice search/actions.. just press the microphone symbol in the Google search bar on your homescreen, or alternatively from the Google Now screen.
Isnt there supposed to be a female voice that responds with an answer? I know i can ask a question but the answer comes back in text.
Depends on the question. Many will give you voice answers if they are straightforward enough questions. Try asking it a simple math problem or to convert currency or if the Yankees won today or... etc etc.. lol
Here are some cool examples as well: How to impress your friends: 40+ voice searches on Jelly Bean - YouTube