In order to start tracking metrics with your clients, you must first enable them in your trainer account.
Click on the Metrics menu on the sidebar and you will see a screen similar to this one with all of the Global Metrics (those created by Coach Catalyst) as well as your personal metrics you have created.
Use the checkboxes next to the individual metrics to enable. Each metric that is active will be available for both you and your clients to start tracking.
Any metric that is NOT checked will not show up in your client's profiles.