Check out the leaderboard to see how everyone is doing in your contest. The leaderboard will only show the players in your contest. So if you're in a "play from home" contest, you will see all other players competing in the "play from home" game. Players competing at a participating location will only see players at their specific location, excluding the weekly national game in which all participating location players will compete for large prizes on a national leaderboard. Even though you may be playing a contest based on the same sporting event, you are only competing for prizes against the players in your contest and that is why they are the only players that you see.
If you are in a group (or 2 or 3), you will see tabs at the top of the leaderboard with your group name(s). If you are in a group with another player that is not logged in to your contest, you will not see them on the group's leaderboard.