Here is the process of how to customize Agency page sections. Click on the customize option on the top bar, a left sidebar appears with the list of sections (Header, Footer, etc..) along with the pages that are present in the theme and you can see the edit icon on every section on the pages click on the edit icon of the section you want to edit.
After clicking the edit icon, a left sidebar displays customizable options of each and every element that are present in that selected section now you can start editing.