Thanks for your help, Trevor. I finally got the thing working. And in case anyone else ever gets one, here's what I did: (the router has to have the Sveasoft firmware to do this manually)

-connect your wireless NIC to the router
-went into the router admin, wireless > WDS
-this is where I went wrong. instead of P2P, I had to enable one of the WDS fields for LAN. Then just put in the MAC of the extender
-connect your wireless NIC to the extender
-go to the extender's admin, put in the info for the router including MAC
-done

Question: The one thing I'm not certain about is this: should the SSID on the extender match the SSID on the router? I wasn't sure if they were supposed to look like one network or if you were supposed to connect to one device or the other.