Leaderboards can be found at the bottom of the Lightning Rewards page, next to the Tier 5 Awards. To qualify for the Leaderboard, you will need to fight your way to Tier 5 and gather enough Lightning to climb over those ranked above you.
Tapping on the yellow "Leaderboards" button will open up the full Leaderboards, as well as two additional tabs: Rewards & Hall of Fame.
Leaderboards: Taking a look at the Leaderboard shows the top three with the most Lightning to the left and the top ten in a list to the right. At the top of the Leaderboard, there is a timer counting down until the end of the season and the information button to the right of it.
Rewards: Climb the ranks to place and receive a prize at the end of the season! Each player who places in the top 10 will receive a coin prize.
Hall of Fame: This feature is coming soon! As seasons progress, the top placing players will be added to the Hall of Fame.
The Information ("i") Button: If you ever have a question about rules, or how a particular feature works, look for the "i" button. In slot games, it'll in the lower left, between the bet level and home button. In the case of the Leaderboards, it's located next to the season countdown timer. Opening it will reveal a quick info box on how to get on the Leaderboards and what happens when you do.
For more information on how seasons work, please check out Lightning Link Seasons.