This tool only works for cracking wifi passwords. And, of course, it´s free. But remember that you only can use it if you have permission for that.
Install and open the app. You will see a list of the wireless networks.
Choose a Wireless network you want to crack and select the method like you see in the image:
Configure the type of attack you want to use (more complex, slower) and click Add to queque
Now you have to wait for the attack finishes.