The examples in GitHub are for Android Studio: they can be directly imported once the Android Studio plugin is installed (File > New > Import Digi Sampleā¦) or downloading/cloning from GitHub.
Those using our APIs need to use our Android SDK Add On (the SDK Add On for ConnectCore 6, you cannot find) already installed. To have everything ready, my recommendation is to install all the needed software listed in our Get started, even better, you can follow the entire guide at http://www.digi.com/resources/documentation/Digidocs/90001945-13/default.htm#concept/android/c_get_started_with_android.htm%3FTocPath%3DDigi%2520Embedded%2520for%2520Android%7CGet%2520started%7C_____0