A complete step-by-step instruction to both sw and hw installation can be found here. Below is a short description of how to connect ThermIQ-MQTT to the heatpump.
First step to install ThermIQ-MQTT in your heatpump is to turn off the main switch and open the front to locate the main control-board. The main control-board is located on the front behind a black plastic cover. On the top left side of the board you will find a connector labeled EXT to which you should connect the ThermIQ-MQTT. The connector is not polarized and can be reversed, please check carfully with the pictures here to make sure you mount it correctly.
If you already have another expansion board connected to the EXT-port then you should first disconnect it and connect it to the similar port on the ThermIQ-MQTT before connecting the ThermIQ-interface to the EXT-port.
Attach an USB cable and an USB Power adaptor able to deliver 1A to ThermIQ-MQTT . Put on front cover and turn on the main switch.
One way to power the ThermIQ-MQTT is to put a power outlet or a switched pwer supply on the DIN rail in the heatpump.