Airport Express as an extender

I currently have an AExpress cabled to my netgear router which inturn is connected to my dsl modem. Both Pc's and MBP work fine but signal does not reach all areas of the home. Bought a second AE to use as an extender but don't seem to be able to configure it. Get nothing but a flashing amber light. What steps need to be taken to add it to the network as an extender. I can't find anything in the Airport Assistant utility to use to set it up as an extender? Thx