New to vesc confused

Hello! 

I'm new to vesc and haven't really coded.

i do understand how i could get things to work, but i don't understand how to do it.. 

so i would like to add this to my vesc 

https://vesc-project.com/node/3351

But how can i write new data to my controller? do i do it inside the vesc tool or what?

Thank you!