At the customize page, you will see available sections in the "Sections" tab.
You can edit an available section by clicking it. Or you can also add a new section by clicking "Add section" button.
Then choose a section you want to add then click "Add" button next to section's name.
Note: all sections in Precia theme have the common settings such as "Background Color", "Section Gutters"
1. Background Color:
Help you set background for a section.
2. Section Gutters:
"Section gutters" will help you control the distance between the sections.