Don't connect propellers yet! Go below and downlaod the multiwii code. Open that code in Arduino IDE. Connect the FTDI programmer to the PCB. Compile and upload the code. The code is not the usual MultiWii code. Is adapted to work witn NRF24 radio connection and to contero brushed mosfet with PWM signal instead of ESC control. So, not any MultiWii version will work, only the code below.