You need to install PostgreSQL on your computer; this installation is recommended because some commands of the Postgres add-on require PostgreSQL to be installed. Besides that, it's a good idea for your development database to be similar to your production database; this avoids problems between these environments.
Next, you will learn how to set up PostgreSQL on Mac OS X, Windows, and Linux. In addition to pgAdmin, this is the most popular and rich feature in PostgreSQL's administration and development platform.
The versions recommended for installation are PostgreSQL 9.4.0 and pgAdmin 1.20.0, or the latest available versions.
The Postgres.app application is the simplest way to get started with PostgreSQL on Mac OS X, it contains many features in a single installation package:
PostgreSQL 9.4.0
PostGIS 2.1.4
Procedural languages: PL/pgSQL, PL/Perl, PL/Python, and PLV8 (JavaScript)
Popular extensions such as hstore, uuid-ossp, and others
Many command-line...