When your devices are set up, it’s time for automation. Home Assistant offers a few built-in automations – Use the automation component to set up your own rules, for the most part.
If you added a random sensor in the previous step then you can use that sensor for your very first automation:
automation: - alias: Check sensor value and show notification trigger: platform: numeric_state entity_id: sensor.random_sensor above: 10 action: service: persistent_notification.create data: message: "Sensor value greater than 10"
For further details about automation, please take the next step or the automation documentation.