look in "plugins" under the options menu/dialog set. There should be one for "UPnP".

If you've already manually forwarded your ports, then you don't need to do it with UPnP. I'd recommend disabling the UPnP plugin entirely and saving yourself a little bit or memory. That's what's throwing the errors (The errors specifically mean that the router won't override manually set port forwards using automated methods like upnp, which is a "correct" behavior, and you should be glad it does it that way).

What that'd be useful for is if you wanted to auto-map your ports on your router dynamically. Basically it's supposed to be an idiot-proofing mechanism -- just turn on upnp and let it do all the work (there's other reasons for it too, but many consumer routers don't support it yet, at all, and most people don't want to use it anyway).