You can edit the details on a Haystack card through the 'Edit' screen. Tap on the card you want to edit and tap the 'Edit' button at the top right to change the details.

Please note that the 'Edit' button does not appear on cards that have already been verified by the person who owns the card (unless that person is you, of course).

Once you finish editing, tap the 'Save' button at the top right to save changes.