There are a few different ways you could do this.
The “correct” way - which is to say, the one that would have the fewest side effects to worry about - would be to apply spatialization directly to the relevant channels. This isn’t something you can do through FMOD Studio, however; you would have to use the FMOD Core API to attach the DSP to the relevant channel or channelgroup and feed it 3D attributes from your game’s code.
There is an easier way, however, and one which can be done in FMOD Studio. I notice your mixer contains one group bus for each of your players. You can’t put a spatializer effect on a bus because buses don’t have 3D locations in the FMOD Studio AI, so they don’t have 3D attributes to pass to a spatializer effect. However, if you add a pre-fader transceiver effect to each of these buses, set them to transmit mode and set each one to a different transceiver channel, you could then create a series of events corresponding to those buses and containing transceiver effects set to receive, each of which is set to the same channel as the transmitting effect in the associated bus. Because instances of those events would have 3D locations, they would have 3D attributes to pass to spatializers, allowing you to spatialize those signals. (You would, of course, also need to set the outputs of the buses to -oo dB, or you’d get a duplicate of the signal that isn’t spatialized as well.)