Simply prepare the jell-o according to the package directions, except replace half the cold water with cold vodka. Pour one layer, let it chill, and then prepare and pour the next layer. Be sure to let the 2nd and 3rd layers come to room temp before pouring them onto the previous layer, so the new layer doesn't re-melt the old layer.
For the white center, it's just unflavored gelatin prepared with 1 large can of sweetened condensed milk in place of some of the water. Don't be grossed out by milk in jell-o. You can't taste it at all, I promise. Honestly, I couldn't find a good recipe so I just winged it, and it came out perfectly.
