Visual Studio 2012 implement unit test to existing project

Help me get understanding in Unit Testing and from a Unit-Test-Beginner view let me understand how I step-by-step implement Unit Test and Fake. In this work I need more understanding in how I should refactor and inplement Interfaces to my existing code. The existing code is working and have a manually created testbench. The purpose is to learn how to develop test-driven-development with this code. The code is mainly written by me and I have just small part that other have developed. I have sourcecode to all code and documentation on all used dependencies. ( At least, I belive I have all the code ;-) The project is Subversion controlled and ankhsvn used as plugin to Visual Studio 2012. I have today tested to change to VisualSVN just to test another "flavor" of the same subversion integration. Some guidelines mai be needed in efficient Subversion and Team-coding-control. The team uses Resharper 8. This has med the team create more "best-practice-code" because the Reshaper coding guidelines. Some refactoring is already done with Resharper tools. I need to get this explored alot more. The main code is only one class containing 50 methods/functions and uses the class to create 20 methods in a dll. The class methods is both own-written code and overrides to code ( manily XML and XML Dsig functions needed to be changed from .Net) This first project is just an introduction and this can be a longer term relation. I need a "code-sherpa" that helps me to create better code and testing.