To Edit a card’s details, tap the name  itself. On the iPhone, this will take you straight to the Edit screen. On the iPad, this will show the card details on the right-hand pane. To Edit the card, tap the Edit button on the top left.

You will be presented with a screen such as the one shown below.

If the person’s details were originally typed in manually, you can change the values here, scrolling down if necessary. Then tap the Save button.

If the name is one that was initially imported from your Contacts, the situation is slightly different. The Card Name and Extra Information can be changed directly – just tap in the text boxes and make the changes. All of the other fields show information stored in Contacts for that person. When you tap in any of these fields, you will be taken to the Contact app for that person where you can make the changes.