Wifi to wireless bridge on OpenWRT?

I installed OpenWRT on a Linksys E2000 router yesterday and plan on replacing a USB wifi dongle with it for the computer in my bedroom (Ethernet to the room is not an option and the main router is in the living room).

What I’m wanting to do is connect the Router to the existing wifi network and connect the computer to the wifi network via the router.

Crude diagram:

[Internet] --> [Main router] -- Wifi --> [OpenWRT router]
                      | Ethernet                 | Ethernet
                      V                          V
               [Main computer]           [Bedroom Computer]

Does anybody know how I would go about doing this?

I tried this once but really didn't have much success. You should be able to put the wireless on the openwrt router in to client mode and connect it to your wireless network, then just bridge the wireless interface with the switch interface. But when I tried I couldn't get it to connect to my wireless network.