You can't really get there from here without some additional hardware.
Page 13 of the manual indicates there is a single A/B encoder input, and then you select an axis and step value from multi-position selector switches. There are no programmable inputs on that controller where you could 'add' another MPG.
If you are trying to add an MPG on each physical table handle it might be possible to run the two MPG A/B inputs through a 4PDT relay. But you'd still have to choose the selector switch to tell the controller which axis to move. i.e. flip relay and also change selector switch.
Unless you're willing to rig up the MPG's to an Arduino and program it to look for state changes on both MPG's. Then Arduino sees state change on MPG-X and sends A/B encoder signals while also grounding the X-IN terminal. And similar for MPG-Y.
Even then you can't run both axis at once - even if the controller is so dumb it'll drive both axis at once (if the X-IN and Y-IN are both grounded) it'll just move them at the same feedrate. There's no way to get simultaneous motion at different rates.