How to install and enable PostgreSQL database server in Plesk?
Note: PostgreSQL management is only available in Web Pro and Web Host licenses. To manage PostgreSQL via Plesk with Web Admin license it is required to purchase Power Pack / Developer Pack add-on.
Install PostgreSQL database server using Plesk Installer according to this KB article.
Go to Tools & Settings > Database Servers and click localhost next to PostgreSQL.
Specify username and password which will be administrative for PostgreSQL and click OK to initialize PostgreSQL: