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- Extract the module archive which you downloaded from the client area.
- Upload the module to your WHMCS installation.
- Go to the WHMCS Admin backend, click on Setup → Payments → Payment Gateways → All Payment Gateways and activate the gateway.
- Click on Manage Existing Gateways and configure the payment gateway.
- Login into https://dashboard.stripe.com/ and create a webhook: Create Stripe Webhook
You find information about each configurable option here.