Season Leader Board and Team Leader Board or is it that am not aware where to find it.

There are two pages for stats:
1. League -> Player Stats (one of the tabs next to Standings) - this shows you the stats of every player in the league, you can sort by passing stats, rushing stats, receiving stats, etc and order the list by each stat (e.g. to order by most passing yards simply click the "Yds" heading at the top of the table for passing stats)
2. My Team -> Stats (one of the tabs next to Roster) - this shows you the stats accumulated by the members of your team, sorted in different tables depending on the type of statistic. Again, these tables can be ordered.