Access Stripe account at stripe.com Create API keys in Developers > API Keys section Copy Publishable Key (starts with pk_) and Secret Key (starts with sk_) Paste keys into Invoices > Gateways > Stripe Configure webhook endpoint for payment confirmations Test with Stripe test cards before going live Access PayPal Developer Dashboard at developer.paypal.com Create an app in the Applications section Locate Client ID and Secret from your app settings Paste credentials into Invoices > Gateways > PayPal Select Sandbox mode for testing, Production for live payments Configure IPN (Instant Payment Notification) for payment updates