Leaderboards are all created at runtime in this asset. To make a leaderboard you’ll need use the Leaderboard Manager API in your own code. You can either create a board and then get it at a later point or Create and get the leaderboard at the same time. Some examples below:

private void OnEnable()
{
		// Creates a board... if it doesn't exist already.
		if (!LeaderboardManager.BoardExists("Level_01"))
		{
				LeaderboardManager.CreateLeaderboard("Level_01", LeaderboardType.Score);
		}

		// Accesses the made board...
		var board = LeaderboardManager.GetLeaderboard("Level_01");
}

API used:

BoardsExists

CreateLeaderboard

GetLeaderboard

private void OnEnable()
{
		// Creates a board if it doesn't exist and then accesses the made board...
		var board = LeaderboardManager.CreateOrGetLeaderboard("Level_01", LeaderboardType.Score);
}

API used:

CreateOrGetLeaderboard