Click Reporting > Metrics in the top navigation.
Click Track New Metric at the top right.
Expand the categories to choose the metric you want to track, and click the Add Metric button to the right of the metric.
To create a custom metric, click the + at the top right. Fill in the necessary information, then click Create Metric.
Once you begin tracking a new metric, proceed to Updating Metrics to update the data points within each metric.