1. The explanation of the security code is as follows:

(1) Meaning: "Security code" is the encrypted password of the credit card.

(2) Location: There is a seven-digit number in the signature column on the back of the card, and the last three digits are the security code.

2. The steps to add bank card information to your iPhone account are as follows:

(1) Click "Settings" on the main interface of the device.

(2). Open "iTunesStore" and "AppStore".

(3). Click "AppleID". If you are not logged in to your Apple account, you need to log in. (You can ignore this step if you have logged in to an Apple account.)?

(4) Click on the account to display the selection interface, and select "View Apple ID".

(5). Enter the password and select "OK".

(6) Go to "Account Settings", click to select "Payment Information", and set the bank card information after entering.