While many consumer products can be set up using the Interactions tool, other devices like those that use MQTT will need to be set up in the Configuration.YAML file. The code that goes in there will depend on what you are setting up and we will get to that after setting up the Configurator add-on.
You can now access the file system by clicking on the OPEN WEB UI link or through the Configurator menu option on the left.
Now you are ready to edit files for Home Assistant. Next you will find and edit the Configuration.YAML file so that you can add all sorts of fun custom Arduino and MQTT devices to the user interface.