???
Are you refering to this picture?
It says you don't need to connect Positive (Vcc).
Again:
You still need to connect the remaining three wires.
You can cause damage to your device if you do not use a 5 Volt-RS232-to-3 Volt-TTL serial adapter.
Additionally:
To be clear, during OpenWrt install the Wiki says your router IP will be set as 192.168.1.73 (see Wiki example).
Again, are you following the WIki installation instructions linked above?