Karma Contests are unlocked at level 10 and pit you against other players in a timed competition of who can perform the most of any particular set of actions on your farm! These actions include the usual things you're already doing on your farm such as swatting Spidermites, using Guano, producing items from contraptions, or completing jobs from your Job Board!
The Karma Contest button has the goat Budhi on it and is above the Store button on the bottom left of your screen. Tap on it and you'll be brought to your current standing in the Karma Leaderboard.
At the top, you'll notice four icons. Let's visit their screens from left to right.
The ACTIONS screen will display the current actions you need to perform to earn Karma. Some actions may require you to perform an action a set number of times before you receive any Karma.
The RANKING screen will display the leaderboard with your current ranking. The leaderboard is also colour coded - green is for Emerald, which is the top rank, then follows Gold, Silver and Bronze. Players that aren't ranked are listed in a beige colour.
Perform more actions to climb the leaderboard, but be careful not to fall behind! The Leaderboard is updated periodically, so don't get caught up watching it when you could be earning Karma! (Please note: Leaderboards are not final until the contest is over.)
The PRIZES screen will show the rewards for each tier from Emerald down to Bronze. Scroll through them using the arrow buttons.
The TROPHIES screen will display your Trophy and Crown collection, as well as your placement in the previous contest. If you were in a winning tier, your placement will be displayed by the appropriate colour and a trophy/crown icon.
Karma Contests occur at least twice a week, so compete strategically and you'll be sure to win EMERALD!