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.
It is relatively simple to incorporate tinyusb to your (existing) project
1. Copy core folder /**tinyusb** to your project. Let's say it is *your_project/tinyusb*
2. Add all the .c in the core folder to your project settings (uvproj, ewp, makefile)
3. Add *your_project/tinysb* to your include path. Also make sure your current include path also contains the configuration file tusb_config.h. Or you could simply put the tusb_config.h into the tinyusb folder as well.
4. Make sure all required macros such as TUSB_CFG_MCU are all defined properly in tusb_config.h.