Good you got going

Telling the machine where it is will all depend on how your machine is set up. I think I saw in your xml you do not have limit or home switches so you will just have to move to a position on the table that your work is and set the DROs to that position. For example if you have code that has the middle of the part as X0Y0 then you would place the material on your table and move to the middle of it then zero the DROs in Mach. Same idea if the corner was the zero point, just move to the corner and zero the DROs.
Having home switches can help you pick up again if you have lost position in a run or want to repeat on a second part etc. You can do similar to a homing setup by jogging to the lower left corner and z fully up then press RefAll, that will zero the machine coords and then when you jog to where you want the work coords to be and then Zero the DROs you will have just set up a work offset. That means if you lose position for any reason it just needs you to jog to the extents again then press Ref All then when you ask the machine to go to X and Y work offset zero it will know where to go.
Hood