Here is how to get started with Postgres on Ubuntu.
# Install the packages
sudo apt update && sudo apt install postgresql postgresql-contrib -y
# Create a new user
sudo -u postgres createuser --pwprompt username
# Create a new DB
sudo -u postgres createdb -O username db_name
The connection URL will be:
postgresql://username:password@localhost:5432/db_name
If your password contains a % sign it needs to be replaced by %25.