To archive a field, choose the desired field within an open item or on the column header in table view. Select "Archive" from the "Actions" section.
The field archive can be accessed from within the Collections settings. Click "Field" on the left side of the settings. Right beneath the list that gives an overview of all fields, you have in your collections, you'll find a button called "Archived Fields". Click on it to see all archived fields.
Here you will see all archived fields. On the right side of each field, you will see the option to either delete or restore them.
Please note that once a field is deleted it cannot be recovered. All information you've added to that field in each item will be removed. A confirmation popup will appear. Click "Delete" to permanently delete the field.