CAD to G code help

I am mentor of a FIRST (FTC and FRC) robotics team. We have a minimill that has a retrofit CNC, run by Mach3. We are trying to make a few parts with our CNC so we understand the entire process. We are having trouble getting from CAD to G code. An example part would be this 1.25 dia washer with 0.312 center hole, and 8 (0.140 dia) hole bolt pattern on 0.312 radius. What's the best way to get from drawing - we can do Inventor or now ems or iges to gcode. We are finding LazyCAM to be a bit of a challenge.

thanks a bunch, C