Install it from this update site:
http://github.com/eyala/pig-eclipse-update-site/raw/master
Pig-Eclipse requires an Eclipse with at least Java 7. It has been tested on Indigo, Juno, Kepler and Luna.
Name your pig scripts with the extension "pig" or add new file associations in the Window->Preferences->File Associations page.
Artem Ervits from HortonWorks has written a lovely guide to getting started with Pig-Eclipse that may be useful for new users.
1.1.2, September 13th, 2016 - Add hover information for keywords, Pig 0.15 and 0.16 support, and fix of issue #6 (thanks to brahamim)