Send configuration to device

How do I send configuration messages with mosquitto for a particular device?

device is tektelic kona home sensor

MQTT downlink doc is here:

The format of your payload should conform to the Application Server configuration (protobuf/json), I believe.

mosquitto_pub -t “application/1device/647fda00000020e8/event/down” -v - I wrote mosquitt0_pub based on application id and the device. How do I send the command to this tektelic device?