Desk Customizations

Why the desk customization modules are more confusing and there is not enough information in them to where to put the exact code…can anyone please help me with the charts,graphs,formatter link
But formatter link i got that to put the code in utils.js ,but it isn’t doing anything at all still showing me the same.Is it because of the defaults…

Can you specify what you want to do with mockups, screenshots if possible.

I am learning erpnext and i want to test the c3.js and making graphs…I don’t have an idea where to test them…Although some of the members saying to put them in reports .Will it work???
Thank you