How can I edit the introduction text on a blog page?

Hi all,

I am working with a client who has asked me to edit the ‘introduction text’ on their Reviews page.

The Reviews page has recently been changed to a blog by another freelancer, therefore this intro text is not directly accessible - image shows the text that needs editing on the right and what I see when I access the Default Blog in Themes:

I can access the individual reviews (default blog posts), but the intro text is nowhere to be found in ‘Default Blog’.

Perhaps I am looking in completely the wrong place - please can someone help me to access and edit the text found in ‘Default Blog’ → ‘Customer Review’ page?!

Thanks in advance!

Abi