Beginner problem

(Note: On the Macbook, I have to create a user called "postgres" in
order to use PostgreSQL--at least, that's what I read...)

Actually, it is recommended that you create the postgres user to *run* postgresql as. You can create all the users you want in psql with

create user new_user with password 'my_password';

Then you have to add a line in the pg_hba.conf file. I always create a separate user for each application.

(6) I changed ~/railstest01/app/controllers/friend_controller.rb to be

class FriendController < ApplicationController
  model :friend
  scaffold :friend

Take out "model :friend" and see what happens.