Firstly, be cautious not to connect the two touch terminals together, it may damage the transistor.
The circuit can be manipulated in various ways to sense for a finger touch at the touch terminal. One of the ways can be to take a wire from the collector of the transistor and give it to the Arduino(make sure to use a lower voltage battery). When the transistor is off(no touch), the voltage at collector terminal should be at a higher voltage level and when transistor is on(touched), the voltage should be at a lower voltage level.
You can check for the typical values that occur at some of the points in the circuit using a multimeter and decide how you can use these points to give input to the microcontroller.