Firewall2 config

Hi, I want to activate the firewall in Suse 8.0 Pro. I use my laptop at work and home. I have just one ethernet interface eth0. At home I have a ADSL connection (modem connected to a linksys router that functions also as a 4 port switch to my home network). IP address is given in both situations (home and office) by dhcp server. What should I configure as internal and external interface in yast2 - security - firewall ? I just want to enable ssh service on my machine. Thanks ./ luis oliveira