Hi Mauro,
have a look here: Cumulocity IoT Tips and Tricks - MQTT cheat sheet
The topic you need to subscribe is “s/dc/myTemplate” if “myTemplate” is your template id.
Btw. event it is suggested to upload the configuration on request to C8Y you can much easier update the text-based configuration using the static template 113,“configProp1=val1\nprop2=val2\n…” on “s/us” topic especially if the configuration it not very big and only uploaded & updated on agent (re)start.