Step 1: Select an event such as irrigation that did not occur in a specific year on your field. Click No to indicate it did not occur.
If you have never done that event on that field, you can also check the box that says "I have never____this field" and it will remove that event from all years for that field!
NOTE: If you accidentally mark an event as did not occur, you can re-add it by clicking on the toggle in the did not occur section at the bottom of the event list for the given year.
Clicking on the toggle will open the list of any events you selected No or I don't know for. From there, you can click on the event you need to add back in and fill out the event form.