In order to create a PostgreSQL user you should go to your cPanel -> PostgreSQL Databases interface.
In the Add New User form enter the username and password. Note that the username will always include your cPanel username as a prefix.
Then you can add the newly-created username to an existing database. For this purpose use the Add User to DBform. All you need to do is select the corresponding database and user and then click the Submit button.
If you have any PostgreSQL problems, ask your host for assistance. SiteGround offers the best Postgre hostingand we'll assist you with any Postgre-related questions/problems you may have.
cPanel is easy to work with when you have the right host to support you. If you need a reliable partner to help you manage your website with cPanel, check out our cPanel hosting services!