tinyusb uses github as online repository https://github.com/hathach/tinyusb since it is the best place for open source project.
If you are using Linux, you already know how to what to do. But If Windows is your OS, I would suggest to install [git](http://git-scm.com/) and front-end gui such as [tortoisegit](http://code.google.com/p/tortoisegit) to begin with.
After downloading/cloning, the code base is composed of
*repo/demos* is the folder where all the application & project files are located. There are demos for both device and hosts. For each, there are different projects for each of supported RTOS.