React SPA Project with Function Based component

I was trying to set up React SPA in my local. I have done that successfully but the example comes with one REACT component which used the old class-based approach. What changes do I need to make to use the new Function-based components?  

It will be helpful if someone can share the code example/ pseudo codes of all the changes and integrations required to get it running.

Thanks,

Ankan Ghosh