Search for binaries like createdb, createuser, psql, etc. pp. If you cannot find them the chances that Postgresql is not installed are pretty high.

If you got stuck just try to compile Postgres again, start postgres with the postmaster command, test wether Postgres is working by using psql from the shell; install "DBI" and "DBD::Pg" and become a member of Perlmonks. Once I tried RPM's but it didn't work out for me. Therfore I cannot say much about a RPM install.

Hanamaki