The Android app at Google Play:
Regular server versions:
The server requires .Net Framework 4.0. This is usually installed on all Windows computers by default, but if you don't have it, you can download it from here.
If you have an Amazon Kindle, or some other device without Google Play, you can download the app from here:
If your phone runs Android lower than version 3.0, you can't use the latest app version. If so you will need this version: