On FIBA Organizer select Competition -> Competitions -> select the league (e.g TEST) you wish to create a new season for (E.g Test) -> Create -> Season   

In new season -> Write a League season name (do not use 2019-2020, but real name of the league) -> select the year(s) of the season -> select visible -> Start date -> End date -> Choose Parameter set

->add or remove additional parameters and press save