Internet Sharing?

[Jack Countryman]

Since I've got a cable internet hookup, but more than one mac, I was
interested in the built-in 'internet sharing' in OS X.  I've put an extra
ethernet card into the mac, and both are recognized.  I can connect to the
net via either one.  But when I hook an additional mac to the second
port...even with sharing 'on' where it says its sharing the internet via
that second port...the additional computer doesn't get a connection.  If I
use the card...the lights do not flash, suggesting there is no ethernet
signal being transmitted (yes the card IS GOOD...I can switch the cable and
connect to the net via that card with no problem).

So...how does one use this 'Internet sharing' feature?  Thanks.