Editing the contents of each section

Generally, you can edit any content in a section by clicking on it in the Customizer preview.

When you hover your mouse over an element you will see 3 icon buttons that you can use:

• Edit icon (pencil icon) - Click on it (or anywhere on the element) and you will be able to edit the element live inside the Customizer preview 
• Delete (trash can icon) - This will remove the element. This button will not appear for some elements that cannot be removed
• Drag (arrows icon) - This button allows you to reposition elements within the same column. Just drag the element up or down to move it upper or lower in the column. This button will not appear for elements that are not in a column