In your picture it shows that the Gallery sees your lot as Generic. Switch to that first, then place the lot. Once placed, go to Build/Buy and to that area in the upper left corner where you can change lot name, add lot traits and change the venue (which is what you want) and change it to whatever type of lot you want it to be. Make sure you save it before leaving Build/Buy, otherwise the lot will revert back to what it originally was (in your case Residential). Perhaps that was your problem?