This guide will walk you step-by-step on developing your first IOIO application!
This guide is incomplete! In the meantime, check out this tutorial from SparkFun
This part is not specific to IOIO. You'll need to follow the instructions on this page. It is highly recommended to install the Eclipse IDE + ADT plugin. Also make sure to install the SDK components relevant to the Android device you will be working with. If you are new to Android development, this tutorial should get you up to speed. Make sure you are able to run the HelloAndroid app on your actual device and not only on the emulator before proceeding.
IOIO should be powered by an external DC voltage source between 5V-15V.