smcculley posted a useful example in the IO Forum:
I have had some requests from people to share my code to talk to Adafruit IO using MQTT and being able to trigger two LED’s.
Note that I am using the latest AdafruitIO MQTT code from GitHub, as it has the latest fixes available: https://github.com/adafruit/Adafruit_MQTT_Library
In Adafruit IO, I created two feeds, called ledone and ledtwo, and added them to a group called leds. I then created a dashboard with two toggle switches, and tied them to the feeds (one to each, obviously) using the default ON and OFF button text.
Check out the post for more details. Thanks for sharing!