Question About Page Editing…

Okay. I am currently using Gridsby free version theme. My home page is set to show a grid of posts on the page when opened.

But when I click on edit page, there is nothing on the edit screen that allows me to edit the grid style of the page.

In other words, why is it that what is seen on the page when opened is not available to be edited on the edit screen of that page? I mean, it’s a page, right? Shouldn’t the composition of a page, the setup, shape and style, be edited from the edit screen of that page?

Very confused.