.pgpass starts with a dot and therefore is hidden from view by default in most file managers, but you should be able to access it through Terminal. You probably don't need the
.pgpass file, so it may be a good idea to delete it. If you do decide to keep it, edit the password file according to the documentation and run
chmod 0600 ~/.pgpass to fix the permissions.
PostgreSQL user accounts are independent of the operating system, but remember that unless specified on the command line,
psql will use the current user's system username as both the database name and PostgreSQL username; an error will occur if a database or user by this name does not exist on the database cluster. To add users, run
psql as the
postgres user, then use the
CREATE ROLE or
CREATE USER SQL commands. Unless the users will connect to the same database, you may want to create databases for each user to avoid errors.