I've updated the getting started guide to include installation of @Paul Stoffregen's Virtual Serial Driver Installer if you use a version of Windows older than Windows 10. If you ordered a TinyFPGA B2 board and are planning on using an older version of Windows, you will need to install the driver in order to program the board.
Windows 10 has a brand new USB serial port driver that works for all CDC class USB devices (USB serial ports). Older versions of windows don't do this because some devices aren't exactly compliant to the CDC class driver and needed special workarounds. The new Windows 10 USB serial driver gets around this by relaxing its standards a bit and letting devices misbehave a little bit. This allows them to default to using the universal driver. Paul's installer installs an INF file that tells windows that any CDC class USB device that doesn't already have a driver specific to its VID and PID can use the generic USB serial port driver.
Paul went through all the work to make this installer and get it signed. Not only does it work for his Teensy boards, it also works for everyone else that makes a generic USB serial device with a different USB VID and PID. Thanks Paul!