first off, what kind of MK1 board do you have (pix help)? Some use the same kick harness as an MKII/MK3/UMK3/WWF.
As for adding the run button, well you have to drill your control panel for the button hole (hopefully you cut a new piece of wood and dont mess up the factory wood/metal) then the kick harness plugs into your UMK3 board and you run the wires to the LP, LK, and Run buttons for both players.
And you need the wiring harness based on what game youre going to run, not what game you currently have:
http://www.jammaboards.com/store/mortal-kombat-2-4-killer-instinct-jamma-kick-harness-midway-h1.html