Enable fire_event for 433mhz device

Configuration
1

I have two temperature sensors (433mhz) which identify themselves as Viking 02811. I have added them to HA and values are displayed in graphs. But there are no events to react on.
Reading the documentation, I find this text, talking about the fire_event parameter. How to I set this?

2

If you have the state of the entity to show in graps, you can react on state changes. You don’t need events for that.

3

I solved this by creating a template binary sensor with the two temp sensors. If any of the temps are warmer than -15 C the sensor turns on:

  name: freezes_temp_too_high
  state: "{{ (float(states('sensor.termometer_frys_nere_temperature'))) > -15 or (float(states('sensor.termometer_frys_uppe_temperature'))) > -15 }}"
  device_class: problem

Then I used that sensor in an Alert-automation:

freezes:
  name: "Freeze alert"`
  message: |+
    Frysarna varma!`
    Termometer uppe: {{ (states('sensor.termometer_frys_uppe_temperature')) }}
    Termometer nere: {{ (states('sensor.termometer_frys_nere_temperature')) }}
  done_message: |+
    Frysarna återställda!
    Termometer uppe: {{ (states('sensor.termometer_frys_uppe_temperature')) }}
    Termometer nere: {{ (states('sensor.termometer_frys_nere_temperature')) }}
  entity_id: binary_sensor.freezes_temp_too_high
  state: "on"
  repeat: 5
  skip_first: false
  notifiers:
    - pfb

Once triggered, the integration will run every 5 minutes and send me the message. If sensor turns off (temperature it back under -15), I will receive the done_message