Controlling Aduino via Bluetooth

how tried to connect arduino robot to bluetooth serial connection ?

Good one... There is an UART signal available on the 10-pin board-to-board connector.

Perhaps tap into that one, first converting the serial to UART?

Pin 10 of the arduino robot ?

No the 10 pin connector connecting the top PCB and the motor board together. A flat cable connects the 2.

I'm not sure which of the 10 pin's you need, but you would be able to connect a serial device to it by first converting the serial to UART, like with a MAX3232 chip.