There are default values here that you can change as you work down the page. Although once you've used a value, stick with it or you will create an inconsistent system. Insert your own values below. the data is used for page generation locally and is not sent back to our servers.
sudo apt install postgresql postgresql-contribsudo password postgres
Depending on your use case you may wish to manipulate Postgresql with a different user.
su postgres
psql
postgres=# CREATE USER tommy WITH SUPERUSER;
You may want to create a database with this user's name
postgres=# CREATE DATABASE tommy OWNER tommy;
To quit psql
postgres=# \q