You will see a radio button labeled at the top of the download table. You must click "Accept License Agreement" to enable the download links. If you do not do this, the links will remain grayed out or lead to an error page.
That's it! You should now have Oracle SQL Developer up and running, connected to an Oracle database. You can explore the various features and tools, such as querying data, creating database objects, and debugging PL/SQL code. sql developer oracle download