To start accepting WeChat Pay payments with Stripe, you will first need to make sure you have "Activated" this payment method in your Stripe Dashboard. You can follow this guide for doing that.
Second, you'll need to ensure that you have enabled these payment methods in the Payment for Stripe iOS app, which is as simple as flipping a switch, as seen below.
Collecting a payment, with a WeChat Pay QR code, is a short 2 step process.
First, enter the amount you'd like to charge, then choose WeChat to generate the QR code & payment link:
Show the QR code to your customer, so they can scan, authenticate and verify:
The Payment app will automatically listen for a successful payment, and you'll be presented with a message when the payment completes.