First, make sure you have install PostgreSQL on your DirectAdmin, or you can install it using this howto.

Lets start…

1. Download the soucre (you can choose another mirror from here)

# cd /var/www/html
# wget http://superb-west.dl.sourceforge.net/sourceforge/phppgadmin/phpPgAdmin-4.0.1.tar.gz
# tar -xzf phpPgAdmin-4.0.1.tar.gz
# rm -f phpPgAdmin-4.0.1.tar.gz

2. You may like to have a shorter directory name

# mv phpPgAdmin-4.0.1 phpPgAdmin

3. Assign proper permission

# chown -R root:root phpPgAdmin

4. Edit file config.inc.php to fit your needs

# nano -w ./phpPgAdmin/conf/config.inc.php

Set $conf['servers'][0]['host'] to “localhost” if PostgreSQL is installed on local machine

You can restore the config file at anytime by typing:

# cd ./phpPgAdmin/conf
# cp config.inc.php-dist config.inc.php

5. Edit httpd.conf

# nano -w /etc/httpd/conf/httpd.conf

After:
Alias /phpmyadmin /var/www/html/phpMyAdmin/
Add:
Alias /phpPgAdmin /var/www/html/phpPgAdmin/
Alias /phppgadmin /var/www/html/phpPgAdmin/

6. Edit DA skin to display a phpPgAdmin link

# nano -w /usr/local/directadmin/data/skins/enhanced/user/show_domain.html

After:
|*if USERDATABASEMAX!="0"|
<a href="http://|domain|/phpmyadmin" target="_blank_">|LANG_PHPMYADMIN|</a><br>
|*endif|
Add:
<a href="http://|domain|/phppgadmin" target="_blank_">phpPgAdmin</a><br>

7. Restart Apache

# service httpd restart

You can now access phpPgAdmin with:
http://www.hostname.com/phppgadmin
or
http://www.hostname.com/phpPgAdmin

Congratulations, you did it

Note:
If you want automatic install or upgrade, you can use this method:

# wget http://www.yourserverguide.com/wp-content/uploads/phpPgAdmin.sh
# chmod 700 phpPgAdmin.sh
# ./phpPgAdmin.sh