Install

_$: apt-get install pgadmin3

Update

We will install a new version of PostgreSQL and a new version of pgadmin too. The current version of PostgreSQL will be reachable on port 5432 and the new one on port 5433

_$: $ pgadmin3 --version
pgAdmin III 1.18.1

_$: service postgresql status
9.3/main (port 5432): online

_$: lsb_release -cs
trusty

/etc/apt/sources.list.d/pgdg.list:
----------------------------------
deb http://apt.postgresql.org/pub/repos/apt/ trusty-pgdg main

_$: wget --quiet -O - https://www.postgresql.org/media/keys/ACCC4CF8.asc | sudo apt-key add -
_$: sudo apt-get update
_$: sudo apt-get upgrade
_$: sudo apt-get install postgresql-9.5 pgadmin3

Check

_$: pgadmin3 --version
pgAdmin III 1.22.1

_$: service postgresql status
9.3/main (port 5432): online
9.5/main (port 5433): online

Accept incoming connections

Our database server is located at 192.168.1.191:5432 and we have to configure it to accept incoming connections from hosts in the same network (192.168.1.0).

/etc/postgresql/9.1/main/pg_hba.conf:
-------------------------------------
...
# "local" is for Unix domain socket connections only
local   all             all                                     trust
# IPv4 local connections:
host    all             all             127.0.0.1/32            md5
host    all             all             192.168.1.0/24          md5

_$: service postgresql restart

Connection

In pgAdminIII go to Add a connection to a server

Name: development
Host: 192.168.1.191
Port: 5432
Service: -
Maintenance DB: postgres
Username: <user>