The best way to do this is open up all three boxes/light fixture. Expose all the wires. First, identify the box that has 110v when the light is off. This is the box where the master will go. To verify the light fixture is where the line from your switch box is going into, you will need to disconnect all the wires in the light fixure. This will remove power from both switch boxes. Test both boxes and see there is no 110v. Then you know that one set of the (hopefully colored correctly) black and white wires in the light fixture are from the switch box. Now, test those wires and see which is which. (quick suggestion, take a photo of before so you have an easy way to rewire things and see where you originally came from. Also, good to have when asking around here).
The directions for wiring from GE are not super helpful unless you have #1. However, it is doable in other situations. The main reason GE can’t make the switch the way you suggest is because its not a typical analog switch. The neutral is needed to supply the switch with a small amount of power used to keep the switch active. If the switch is not active, its useless as a smart switch since it would never know its being asked to turn on. I am going to assume @chef_32’s problem is he has it wired without the use of a neutral wire. It may be a white wire, but probably not neutral. @ron, I have read of people who use these switches (actually, the older models) without a neutral, but you must have a standard incandescent bulb to draw the power. They do sell switches that don’t need the neutral, but again, you have to use incandescent bulbs.
Hope that helps some. It might just confirm what you already know. No neutral, no go. Sucks, but I think its kind of a physics thing.