As a potential Buttplug Developer, the first thing you should do is...
BE A BUTTPLUG USER!
This means becoming familiar with Intiface Central, the application that the users of your apps and games involving Buttplug will use to manage and connect to their hardware.
Before embarking on the developer guide, I highly recommend reading the Intiface Central Quickstart and going through the steps to set up the application. Much of this developer guide assumes you'll be connecting examples (and later, your own apps) to Intiface Central, so it's good to be familiar with it up front.