How to edit a black space whioch doesnt show in 'edit' form

Site URL: https://www.blewburyselfstorage.co.uk/

Hi All, 

Im trying to add an image to an empty area of the website but when i go into edit it disappears and i can only edit the blocks above and below which are already 'full' and occupied. 

the website is below just scroll down to find the big black empty space which i cant seem to edit! any help appreciated!

Lucy

https://www.blewburyselfstorage.co.uk/