To enable this functionality you need to provide your own Google Analytics Tracking ID which should look something like UA-000000-01. Pro users can enter this in their account settings and team owners do it on the team settings page.
Don't have a Google Analytics account?
1. Sign up for free at http://google.com/analytics
2. Create a new property for Slides using the Google Analytics dashboard (step by step instructions)
3. During setup you'll be asked to provide a "Website URL" or "Default URL", please enter "slides.com"
4. Once the property has been created use the following guide to locate your tracking ID: https://support.google.com/analytics/answer/1032385?hl=en
A single tracking ID is shared for all members of a team. This means that views on all team member decks and profile pages are sent to a single analytics property, as opposed to having each member specify their own.