Scheduler gives you the option to schedule jobs using SQL developer. It's at the very end of a very long tree list. If you connect to your database and expand a SCHEMA, you'll see SCHEDULER at the very bottom.
There's a wizard interface that will walk you through the entire process of creating a new job, or you can use the traditional forms to create and alter existing jobs and schedules.
Tip
All the objects under Scheduler in the DBA navigator are for objects that are owned by the SYS user and that can be created and modified only by users with DBA privileges. Other objects are listed under Scheduler for users in the Connections navigator.