Unable to connect to a server

I'm a newbie, using the Mac platform.

I've installed PostgreSQL on a server and can run PostgreSQL based
application from that server with no problem.  But when I try to
access the DB on a different computer, pointing to the server for the
log in, I get this error:

A connection to the specified xTuple ERP Server cannot be made. This
may be due to an incorrect Username and/or Password or the server in
question cannot support any more connections.
Please verify your Username and Password and try again or wait until
the specified xTuple ERP Server is less busy.
System Error
QPSQL: Unable to connect

 From doing some reading, I think the solution is to change the value
of  listen_addresses to '*'

But I don't know where to do that.  I'm using pgAdmin3.  Can it be
done there?  Or do I need to use Terminal?

Any help would be appreciated...

Steve
-----------------------------------------
Steve Henry
San Diego Mac IT
http://www.sdmacit.com
760.546.8863 Cell