SQL Developer code formatting
I did a google search for the phrase "sql developer code formatting", and the first hit was this:
http://www.thatjeffsmith.com/archive/2014/03/how-to-make-your-code-look-like-steven-feuersteins-in-oracle-sql-developer/
Have a read through that blog post from Jeff Smith, product manager for SQL Developer. That should explain what you need to do.
Edited to add picture of the relevant options.
Has actually moved in v17.4
Can be found in: Oracle SQL Developer -> Preferences... -> Code Editor -> Format
and Optionally -> Advanced Format -> Custom Format