The board is a clone of a Digispark USB development board with an ATtiny85 microcontroller. For your convenience, this board has been pre-flashed with micronucleus v2.04a (an Arduino IDE compatible bootloader). In other words, you can program this board using the Arduino IDE, if you configure the Arduino IDE accordingly (Use Digispark default - 16.5Mhz). (Caveat: the instructions found above do not seem to work out of the box with the latest micronucleus bootloader, but I'm sure you can figure it out)
If for some reason you want to install a different bootloader, that is also an option, but you will need to reflash the bootloader using ISP. For this purpose you can e.g. use another Arduino board (Arduino Uno or Nano will work for sure)