Couldn’t get the file to print from the SD card how, in the LCD screen, what happened?
You can always generate the part in fusion and use ESTLCAM as your CAM processor. If you want to use fusion for everything try this thread, http://www.vicious1.com/forum/topic/fusion-360/.
A post processor is what formats the gcode properly for the board that will run it. Things like // or ;, and how the coordinates are sent one at a time x then y then z, or xyz.
Luckily someone has taken care of that and it is fully functional as far as I know for fusion, and found in the linked thread.