In OpenTX companion's preferences window, make sure the proper firmware is selected (OpenTX for FrSky Taranis, or OpenTX for Taranis Plus according to the hardware you have), and the language / options match your preference, then click the top Download button and select a location for the file. This will automatically build and download the latest available version of OpenTX for Taranis. Close the Preferences window, and select the Burn -> Write Flash memory command. Make sure your radio is powered off and connected. Browse for the file you just downloaded. It will be recognised automatically and the version will be displayed. If you wish to replace the radio's splash screen, you can either load one from a file or select it from the available library, and click the "Substitute image in firmware" box. Click "Burn to TX". Once the progress bar is done and the success prompt is shown you can dismiss it and disconnect your radio :) If you get an error about the dfu-util executable not being found, open the flashing tool settings with the Burn -> Configure menu item. Browse for the dfu-util executable, which should be: On Windows: In the OpenTX companion installation folder (by default C:\Program Files\companion9x\dfu-util.exe on 32-bit systems, and C:\Program Files (x86)\companion9x\dfu-util.exe on 64-bit systems). On Mac OS: /opt/local/bin/dfu-util.