Postgre and Redhat 7.0

Hello everyone I am a complete newbie to postgre. I am having a problem
logging into the postgre user file in RH 7.0 when I try to do su postgre
I get a bash prompt. Also on the postgre website the directories being
used are different than the ones RH has set up where the documentation
on the website suggests /usr/local/psgl/bin/psql  RH has it setup as
/var/lib/pgsql is it ok to use the lib directories for this or should I
make directories and relocate the executable and othe files psql need.

By the way I installed these as rpms from Redhat and they did a lot of
things automatically and I have no clue as to what goes where. How do I
log into the user postgre that redhat made for me. Are there any docs
out there that will show me how to do this I have searched the net far
and wide no luck and I cant seem to get the info from any of the man
pages and docs that were included with the rpm's or am i looking in the
wrong place.

Any help[would be greatly appreciated I am using Postgre  7.0.2 and are
there any websites out there that anyone can refer a clueless complete
newbie to get up and running Postgre on a RH distro.

Thanks in Advance

SB