authentication totally baffles this novice

I'm trying to use postgresql with the horde suite and I feel like I'm pushing a
string.

Running with a Red Hat 9 system with all the patches.  Start up postgresql to
create the initial database.  everything successful.  Try to list database
tables from postgres account works.  Try to do it from any other account and I
get: psql: FATAL:  IDENT authentication failed for user "horde"

commandline I was using from other accounts was "psql -U horde -W" and I get the
above error after entering the password.

If I could have a clue please, it would be most appreciated.  Even a simple URL
would do.

many thanks in advance.

---eric