The League Convenors page will draw its contacts from league-level contacts (executive & staff) who have a sort order of 3 or higher.
So, for example, use Manage Site Content and select a league-level site, then go to Basic Features -> Executive & Staff. Add the league (division) convenor to the list and use a sort order of 1, 2, or 3. This person will then show on the right-hand side of the league home page as well as on the organizational list of league convenors.
Each league can have as many contacts as needed.
Hope that helps.