When purchasing apps or media with your Apple ID, most people enter their credit or debit card. But if you'd rather use PayPal to buy apps from the Apple App Store or Mac App Store, it's easy to set up on your iPhone, iPad, or Mac. Here's how.

How to add PayPal as a payment method in the App Store on iPhone and iPad
Before we begin, we'll assume you already have an Apple ID that you use to purchase apps. If not, it's easy to create one. Apple IDs are cloud-based accounts that are valid for Apple services across all your Apple devices.
On an iPhone or iPad, it's easy to add PayPal as an Apple ID payment method from the Settings app. It's worth noting that once you add it using your iPhone or iPad, the payment method will apply to your Apple ID on any platform, including your Mac. Here's how to set it up.
First, open “Settings” on your iPhone or iPad.

At the top of Settings, tap your Apple ID account name.

In your Apple ID settings, tap “Payment & Shipping”.

In the “Payment & Shipping” settings, click “Add Payment Method”.

In the list of options, tap “PayPal,” then tap “Log In to PayPal.”

Next, log in to PayPal using your PayPal account. You also have the option to create a new PayPal account during this step. Once logged in, review the PayPal payment options and click “Agree & Continue.”.

After that, PayPal will be added to your list of payment methods in your Apple ID. By default, Apple will use it to charge account when you purchase apps from the App Store.
How to add PayPal as an App Store payment method on Mac
You can also add PayPal as a payment method for your Apple ID using your Mac.
It's worth noting that if you share an Apple ID across all your devices and have already added PayPal as a payment method using your iPhone or iPad, you don't need to do it again with your Mac. The PayPal option will already be set up.
The easiest way to associate PayPal with your Apple ID on a Mac is by using the Mac App Store, which you can quickly find by opening Spotlight by clicking the magnifying glass icon in the menu bar and typing “App Store.”.

First, open the “App Store” on your Mac, then click on your Apple ID name in the corner.

On the next page, click on “View Information”.

Under “Account Information,” look for the “Apple ID Summary” section. Then click “Manage Payments.”.

On the “Manage Payments” screen, click “Add Payment”.

When the “Add Payment” screen appears, select the “PayPal” logo from the list of payment methods, then click “Log In to PayPal.”

Follow the sign-up process and accept the terms. When you're done, PayPal will be added as a payment option to your Apple account.
Information source: howtogeek.com
