a easy method on posts if you are new to fusions post files, its all in Java so its pritty easy to find and edit things. plus you can code some nifty tricks inside the post too
for a mill turn, when i was looking into it i found the post for a nakamuura mill turn was pritty well done in fusion so is a very good start point. has a nice turrent switch over for multiu turret, multi spindle too and much more you would need ona mill turn
for a nifty trick you can use visual stuio with a free addon,
when you post any code from a program pick the option post direct to visual studio and it will let you see the post code file along side the Gcode so you can find any Gcode section in the post and edit and check. it will also cut down the Gcode it will post out if you have a long operation like surfacing so can check complex operations with ease.
check this video for a much better detail way todo it, and set it up etc