Arduino cnc plotter programme question

I am planning to make an arduino cnc plotter/drawing machine. I have read several tutorials, but I am not sure what programmes I need to use, and how to use them. I am using a Mac computor. Can anyone please help me?

For my plotter I use the Grbl firmware loaded into Uno for the g code interpreter and stepper controller.

I wrote my own code in Processing on my Mac.
See the write up Proxxon MF70 Miller CNC CONVERSION

Thank you for your replies.
I think your tutorial may help me.
Thank you for your help.