You can access the Comparison Tool from the following locations:
From the Document Toolbox
Navigate to a page in the document.
Click Document Toolbox.
Click Compare Versions.
From the Document Manager
Click Scroll Documents from the Apps section in your space sidebar.
From the Document Library, click the document card of a document.
From a page in a document, click Document toolbox and click the cog icon.
Navigate to the Comparison Tool
Click Compare versions next to the Save a version button.
In the Comparison Tool, select the version with which you want to compare against.
Scroll through the result to view the changes or use Previous and Next in the bottom action bar to navigate between the changes.