Map comparison is only available on the web app
Map comparison is a premium feature. In order to activate you will need to upgrade your farm to Pro. You can find instructions for doing this here. A free 14 day trial is available to allow you to see the value of this data for yourself.
Use maps comparison to view two maps side by side to see if treatments and management decisions are making a difference with 3 years of historic data.
At the bottom of the Field Health section you will see a button that says ‘Compare Two Maps’. This opens a modal where you can select two dates of imagery and view them side by side.