Yes, that link at dd-wrt is certainly one way. However, I find it often confuses newbs. Many end up stomping the wireless client configuration in their clumsy attempts to configure the wireless AP. I find it much easier (and much more obvious what’s actually happening) if you break it into two steps. Also, there’s a lot of extraneous stuff in there you don’t need, like refs to AP Isolation, DNSMasq, SPI, Advance Routing, holy crap, no wonder ppl routinely mess it up, it should be rewritten imo.
Here’s the “simple” way, fwiw.
First configure the router for "client bridge", and ONLY once that's working, update that same configuration to "repeater bridge".
Assign the router a static IP in the same network as the primary router (and not in use by its DHCP server). So say the primary is 192.168.1.1, perhaps make the repeater 192.168.1.2. Save and reboot. Update the wireless mode to "client bridge". Save and reboot. Update the wireless security to match your primary router (SSID, wireless key, etc.). Save and reboot.
If done correctly, you should be able to support WIRED clients at the repeater.
DO NOT PROCEED FURTHER UNTIL THIS WORKS!
Leaving the client bridges settings alone, change the wireless mode from "client bridge" to "repeater bridge". Save and reboot. At the bottom of the wireless setup add and configure the virtual SSID. Save and reboot. Go to wireless security and you'll see a second section for the new SSID where you can add wireless security. Save and reboot.
At that point you should have support for both WIRED and WIRELESS clients at the repeater.
Simple, right?
NOTE: If you use the same SSID and wireless security for both routers, you'll also have a form of wireless roaming. Wireless clients will automatically select the AP w/ the strongest signal. Not a big advantage for fixed devices, but perhaps useful for portables.
Trust me, it’s MUCH easier and less prone to errors if you take it in STEPS!