There are two temperature sensor inputs on the board, and two thermistors supplied with the eChook nano kit. Each thermistor can be placed anywhere on the car for monitoring the temperature at that spot. The temperature sensed on the ‘Temp 1’ input is displayed on screen in the app, and the other input is just logged, not displayed.
As such Temp 1 will normally be used for motor temperature so it can be monitored through a race by the driver. If possible it is best to secure the sensor directly to the motor rather than to a heatsink for the most accurate reading. Be a little delicate with the thermistors as they are not hugely robust, but have proved fine once secured in place.
One leg of each thermistor goes to ‘Temp 1’ or ‘Temp 2’, and the other leg to ground (0V). They are a purely resistive component, so polarity isn't important.
It may be easier to calibrate the thermistors before fitting them to the car. See the 'Calibrating the eCook > Temperature' section of the documentation