The flashable image available is the one you can get from here: Intel® Edison Products — Software Downloads
Are you using the latest version? If you do, you can install packages from the AlexT repository and if it is not in there you can install the source, if you have questions about how to install a specifically package let us know, sometimes the only way to install a package is with a recipe so you may need to create a custom image.
There is a nice tutorial about playing audio with the Edison board that may help you on this. Let's make some noise (or how to play audio on Edison). Have you checked it?
What is the outcome of using Yocto and what have you tried with this image?