Where can I find my rewards?

For the Apple Card cash back rewards are added to your Apple Cash account.

You can find each cash back entry in the Wallet App under Apple Card's activity report in the Daily Cash button.

Link-> Get unlimited Daily Cash with Apple Card - Apple Support

Apple Card MasterCard offers Daily Cash Back on all purchases/charges of between 1% and 3% depending on the merchant and use of Apple Pay. Using the physical titanium card only offers 1%. Here is a support article that covers the rewards of Apple Card.

Apple Card - Features - Apple

Get unlimited Daily Cash with Apple Card - Apple Support

In order to receive your Daily Cash Back you’ll need to set up Apple Cash in your Wallet App on your iPhone. This article covers the details,

Set up Apple Cash - Apple Support

Once you set up Apple Cash, you’ll want to go through the ID verification process required by federal law.

Identity verification for Apple Card or Apple Cash - Apple Support