There are packages for major platforms. You can install PGroonga easily.
There are separated documents for these platforms. And there is a document for building PGroonga from source.
Here are supported PostgreSQL versions:
If your PostgreSQL is older than them, you need to upgrade your PostgreSQL before you install PGroonga.
See a document for your platform in the followings:
32bit + PostgreSQL 9.5.5-1
64bit + PostgreSQL 9.5.5-1
32bit + PostgreSQL 9.6.1-1
64bit + PostgreSQL 9.6.1-1
You can uninstall PGroonga by the following SQL:
DROP EXTENSION pgroonga CASCADE;
If you're using PostgreSQL 9.5 or earlier, you need to also run the following SQL:
DELETE FROM pg_catalog.pg_am WHERE amname = 'pgroonga';