This guide will help you get started with RetopoFlow 4.0.0α.
To start retopologizing in Blender after installing Retopoflow:
Either click “Retopology at Cursor” or “Retopology at Active”
You can also create a new retopology object yourself or select an existing retopology object, enter Edit Mode on it, and switch to any of the RetopoFlow tools in the toolbar.
Enjoy!
For a more in-depth explanation of the tools and how they work, continue on in the docs.