theming – (Rookie Question) Set background picture only within the text field, not entire page on Drupal 7

How should i make the background image appear within the text field (in context type: basic page) but not the entire web page?

I am using Background Image Formatter, running on Drupal 7 with Bootstrap 3.
Module url: (

I would like to appear within the text field

This is my current config
I am extremely new to web development and Drupal. Apologies if such question offends you. Any answer is appreciated!