Type command where?

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/12/tutorial-createdb.html
Description:

I am at this point in the documentation and I'm told to type a command.

"1.3. Creating a Database
The first test to see whether you can access the database server is to try
to create a database ... To create a new database, in this example named
mydb, you use the following command:

$ createdb mydb"

I know this may sound silly, but "where" am I supposed to type this command?
I'm smart enough to realize that I need a prompt, but in what app or
environment will I find the expected prompt? I started "psql" and get this
prompt:

"Server [localhost]:_"

I don't get a $ prompt, and when I type the createdb command I get no error,
but pgAdmin4 shows no 'mydb' database either.

I think it would be very helpful if the documentation included explicit
steps and screen captures.

Thank you very much,
Chuck Becker