This core will allow you to use BSFrance AVR based boards with the Arduino ecosystem.
At first drivers for the usb-serial (VCP, Virtual Com Port) has to be installed. This applies to Windows only, Mac OSX and Linux users wont have to install drivers (in most cases).
Plug the board to USB and proceed with the driver setup. Then Core files can be installed:
Download and unzip this repository to Documents / Arduino / hardware folder. Note : Documents / Arduino is the default location, if you use another location principle is still the same. If you dont have any Hardware folder in Documents / Arduino create it and unzip the BSFrance repository in it. If you already have a BSFrance folder you can directly drop the STM32 folder in it.
Launch Arduino IDE, select BSFrance LoRa32u4 / LoRa32u4II boards in the Tool / board menu, select the correct serial port in the Tool / port menu. Your board is now ready to use with Arduino IDE.