To display a leaderboard of top ranking users:

1. Add Live Leaderboard module to the page
2. Make sure you're in Edit Mode, from Action Menu, click Manage
3. Select an option such as Experience, Reputation, or Custom Point Types for Display leaderboard for following point type
4. Specify a number of users to show for Display top users

Configure Activities
Users must've earned points to appear in leaderboard. Be sure to award points based on user activities