create a workspace in APEX that has FOOTBALL_MGMT as the default schema, and then create your objects in that schema either using SQL Developer or APEX (or SQL*Plus or whatever other tool you prefer). I find SQL Developer much easier to work with for creating tables, packages, etc. but that's a matter of personal preference.
CREATE USER football_mgmt ...
or you would need to create synonyms (either local or global) for the objects that are owned by the other user.
SELECT * FROM some_other_user.some_table_name