As a complete novice as well , sounds like your possibly missing at least one part of the chain, Computer Aided Manufacturing software, guess you have some sort of drafting program that you have your designs in.

Need to export from there to a CAM program that will generate the toolpaths and Gcode for Mach3 to run the machine.

There are lots of CAM packages out there , most with some sort of free trial, at moment finding MeshCAM user friendly CAMBam seems popular here, theres a lot of others.
After the free trials though be prepared to open your wallet again....

Cheers
Adam