You can record metrics for any action in the Reporting field of the Action Status tab. These metrics can then be viewed on the Reporting page in the Reporting overview chart.
How to set up reporting
1) Publish story
Metrics are only recorded for published stories. You can publish a story through the button at the top-right of the Story page.
2) Turn on reporting
There is also a Reporting slider on the right hand panel which should be switched on by default.
3) Set reporting metrics
Select the action you want to record metrics for. Then open the Status tab in the right hand panel and click the plus symbol next to the Reporting section. This will open a series of metrics with modifiable units and values.
4) View data
And that's it! As your actions with reporting metrics run, the accumulated data will be displayed on the Reporting overview chart on the reporting page. As more metrics are added, more categories will be added to this graph.