This link will only work if you are on the alpha list. Please use the mail link to the left of this post to send me a pm with your google play email address, and I will get you added! From this point on, you will not need to keep an eye on updates in the forums to get the newest version1
You will need to remove your version that you downloaded as an apk, otherwise you will end up two two versions of the app.
All users in beta (accessible through the help menu) will be eligible to join the Play Store Alpha.