Create a new Intent name: addSchedule.

Under Training phrases type: add schedule on 5th July for yourmessage at yourTime and Change the parameters name: a,b and c.

Then go to Fulfillment session under intent. and Enable webhook call for this intent.

Now go to Fulfillment menu undersidebar and Enable the Inline Editor.

Define intentMap.set('YourIntentName', FunctionsName) Functions. For example in this intent I'm using

    intentMap.set('addSchedule', addNewSchedule);

Create a function named 'addTwoNumbers'.

 function addNewSchedule(agent){
      var time =agent.parameters.a;
      var date =agent.parameters.b;
      var msg = agent.parameters.c;

      firebase.database().ref('schedules').push({
          time:time,
          date:date,
          message:msg
      });
      agent.add('Your Schedule for '+msg+' on '+ date +' at '+time +' has added successfully.');
  }

Add const firebase = require("firebase");

Add "firebase ":"*" in dependencies.

Add Firebase key in index.js file.

Click on Deploy Button

Test it.