Where is Google Play Music Player available?

I bought my Nexus 4 but don't have a way of organizing my music other than dropping the files in. I found out about Google Play Music Player but every time I try and download it shows as unavailable. So where is this program available? and why am I not able to use it?

Also, if you know of any better solution for music organization I'd love to know!

Edit: I live in Canada