How do I request a credit line increase

The link above your post explains how to make that request. I’ve copied the pertinent part below:

Request an Apple Card credit limit increase

On your iPhone:

1. Open the Wallet app and tap Apple Card.
2. Tap the More button , then tap Card Details .
3. Tap the Message button .
4. Type a message requesting a credit limit increase, then tap the Send button .

On your iPad:

1. Open the Settings app.
2. Scroll down and tap Wallet & Apple Pay.
3. Tap Apple Card, then tap the Info tab.
4. Tap the Message button .
5. Type a message requesting a credit limit increase, then tap the Send button .

Goldman Sachs will consider your payment history with Apple Card and other credit information to determine whether to grant any request for credit limit increases on Apple Card.1 This means you may need up to six months or more of payment history with Apple Card before Goldman Sachs can approve your request for a credit line increase.

Learn how your initial Apple Card credit limit is determined.