Initial start-up problem

I’m about to feel very stupid…I can feel it.

I’m still a wp newbie. I designed a one-page responsive site with the Zerif Lite theme. When working that site, I would navigate to appearance>customize, and work from there. It was simply a matter of adding and editing the corresponding widgets.

On this theme, I don’t understand how to edit the page. For example: in the demo where it says “clean design and functionality” there shows circular icons and descriptions but I see no way to edit those and no obvious widget to add.