How to access SQL commands

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/13/database-roles.html
Description:

If you have no experience using SQL, you don't know how to access Postgres
SQL functions
Crucially, I need to know about: sudo su - postgres
I didn't at this stage in the documentation.

My path in the documentation was
=> 1.3 https://www.postgresql.org/docs/current/tutorial-createdb.html
=> attempt to *createdb* at the command line
=> failed with createdb: could not connect to database postgres: FATAL:
role "name" does not exist
=> routed to Chapter 21. Database Roles
https://www.postgresql.org/docs/current/user-manag.html
=> attemped CREATE ROLE name at the command line

and, of course, failed.

It doesn't take long to figure out why, but you seem to appreciate fine
detail in your documentation.