Modifying postgresql.org file

It has been suggested to me to increase my work_mem to make queries preform faster. I believe I do this in the
'postgresql.org'file.  I seem to have two of these files:<br /><br /> /etc/postgresql/7.4/main/postgresql.org<br />
/usr/share/postgresql/7.4/postgresql.conf.sample<br/><br /> I believe the second one is an example/sample file (similar
tohow xorg.conf comes with a sample file). Can someone point me in a direction as to where I can learn how to modify
thepostgresql.org file to increase work_mem? I have the O'Reilly book "Practical PostgreSQL" but it doesn't seem to
coverthis topic. I'm fairly confident that I can tweak the postgresql.org file; given that I was successfuly tweaking
myxorg.conf file. <br /><br /> Any help/guidance is very much appreciated.<br /><br /> -Ken