temperature value as a sensor?

[nono9871]

We use an external heatpump in our Wellis Amazonas Swimspa.
The heatpump has a fixed (high) target value and temperature is controlled by turning the heatpump on and off using a homematic switch. Goal is to control everything together with homeassistant, but for that (as far as I understand) the current temperature reading would have to be defined as a sensor. I'm new to homeassistant, so I hope I understood it right.

Regards Marco