CCVAR custom property implementation

Hi, 

I have a requirement to implement a custom property of a component to be used as a CCVAR variable in other pages/components. I have looked at this article https://adobe-consulting-services.github.io/acs-aem-commons/features/contextual-content-variables/index.html but it doesn't really help for the custom property implementation and I could not find any other references for the same. Could you please point me to the correct reference for the implementation of it. Thank You