I don't know how RH sets Pg up, but usually you
should have the daemon running after a successful
ps -A | grep postmaster
If that gives a result it's installed properly.
On a commandline try
That will create a database with your username
After that you should be able to
and end up with a screen like
Welcome to psql 7.3, the PostgreSQL interactive terminal.
Type: \copyright for distribution terms
\h for help with SQL commands
\? for help on internal slash commands
\g or terminate with semicolon to execute query
\q to quit