FTDI and atmega328p-au
BLK is ground. 
CTS is generally not used. I leave it unconnected on my boards.
DTR goes to the auto-reset circuit.

Update:


  Can I let DTR directly connect with RESET ?


Auto-reset circuits use a .1uf capacitor between the DTR (or RTS, depends on which one your cable supplies) and the reset pin. (The exact value probably isn't too important). Without it, the reset circuit is likely pick up noise and randomly reset the Arduino.