Press "set", and use the "+" and "-" keys to navigate the menu. Press "set" again to edit a parameter. Store with "set", or wait about 10s until the menu times out.

Install the thermostat in your installation, as you would with the original firmware. The sometimes difficult task of optimizing the control behavior can be simplified by using logged data. Refer to the README for instructions.

Follow the instructions on the STM8 eForth W1209 wiki page to erase the original W1209 firmware, and program the thermostat binary in the file W1209-FD-forth.zip on the W1209 data logging thermostat releases page. After flashing, make sure it starts up (the display should show the temperature, or "DEF." if no sensor is connected. To initialize the parameters in the EEPROM press the W1209 "+" and "-" keys for about 5 seconds ("RES." should appear).