Tsunami 2 4400

I’m fairly new to using DCC to run my locomotives, and I’m attempting to install a Tsunami decoder into a Key Imports FEF-3.  Prior to, I constructed a little platform to test it...and I got nothing.  No lights, no sound.  I have the system set to #3, which is the default channel out of the package.  My assumption is that I have wired something wrong.  The led anodes are wired to the inputs, the cathodes to the common.  The speakers only have 2 connections.  I have no electric motor handy to provide a load.  My prime suspect is the “ground” connection which I have not connected to anything as the decoder already has connections for the rails.  Where would this connect to?  I include the factory diagram for reference.