To use a template, make a new empty file and set the grblemachine pp in the options.
Save the file in the template folder.
When you start CB with a new file from template it will be set.
Then make your geometry and generate the code, switch to GRBL machine and run the file.
If you make a mistake then GRBLMachine will ask if you want to regenerate the file again with the GRBLMachine PP, if everything is ok grbl will just run.
See pics.
Dave