I am new with the Tstat8, I would like to know if this already includes the temperature sensor or you have to acquire it separately.

The Tstat8 has a temeprature sensor inside by default. There is an optional humidity sensor model and another with a Co2 sensor option, these are not included in the basic Tstat8. You can connect up to eight external temperature sensors to the Tstat8, these are also optional. I will make a note to get some notes and a wiring diagram on there that makes this more clear.