How to implement a 1D silder with the embedded touch sensor

I have a STM32F072RB that came with a touch sensor on it. What I want to do is to use it as a input to implement something like a volume silder. Anybody knows how I can get started? I found some an example from ST where the touch sensor is used as a physic button. However in my case, I think I need to know the touching position, but I don't know how I get extract that information from the sensor.