How do I read a simple touch sensor value from Arduino?
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.