How do i set my linksys router to repeat befw11s4v4

Hello,
If I have two Linksys wireless routers in my house, ( 1 Wireless-G as the Gateway attached to the DSL line, and attached to the main computer, and 1 Wireless-b model BEFW11S4v4 that I want to use as a bridge or as a repeater to send the wireless signal around the attic (2 floors away) and I have connected them via Ethernet, and then connected to the attic computer (not the main one) via Ethernet to Wireless-B, why can I not get connectivity on the attic computer?
If I forgo the Wireless-B router, and connect the ethernet to the attic computer everything is fine, but there is no wireless signal in the attic. (only downstairs where the Wireless-G is.) I believe I can access the Wireless-G and tell it to be a bridge or a repeter (?? I think) but as far as I can tell the Wireless-B is giving itself the same IP address as the Gateway Wireless-G is using, and I don't have an connectivity, so I can't change it! Im confused. Help.