How do I unlock and lock my Apple Cash card?

You mean other than the passcode and biometrics restricting access your phone …

… and the optional biometric lock you can apply to further restrict access to your Wallet app …

… and the continuously updating CVV of AppleCash’s virtual card … ???

Then …. no.

Effectively, everything in your iPhone and/or Apple Watch Wallets are locked by your biometrics.

Not using Apple Pay to complete transactions, potentially exposes your card details to scammers. Using Apple Pay and Apple Wallet is much more secure than physically using the card.

My own line:

The act “most injurious to the security” of your financial cards is …

… withdrawing the physical card from your pocket / purse.