Botmill Axis 2.1 Kit - RAMPS v1.2 Opto-Endstops not working

I got my RAMPS 1.2 firmware setup and I am able to move each axis and the extruder motor with the controls in RepSnapper. I am using the Sprinter firmware.

I made changes to Configuration.h on line 30 to get control in both + and - directions.
const bool ENDSTOPS_INVERTING = true;

As well as commented out line 28 since I'm not using mechanical optos.
//#define ENDSTOPPULLUPS 1

Questions
1. How do I setup where my Home location is for each axis?
2. The opto-endstops are hooked up properly but I don't have an LED on. I am assuming they should be ON when there isn't anything in them and OFF once something enters them, correct?
3. Once these are working, how do I configure them and manage them in RepSnapper? Is this even possible?

Thanks for the help in advance!

The home position for each axis is defined by the location of your endstop. It defines the origin: (0,0,0) of the Mendel. Make sure you follow the right hand rule or your prints will come out mirrored. With the power off, you need to position your endstop flags so that they line up with the gap in the endstops.

My opto endstops don't have LED's. But according to the wiki, the LED in a standard Gen 3 opto endstop should light up when you block the light.

When you move each axis in the + direction, they should move away from the endstop since the endstop defines the zero position. If it moves in the opposite direction, then you need to either reverse how the motor connector plugs into the RAMPS. If you put something in the endstops to break the light like a coin or a piece of metal, the axis shouldn't move in the - direction. If you move it in 10 mm increments, it should stop when your endstop flags reach the endstop.