Go to Configuration -> Plugins -> Stripe and fill in the fields:
Public API key: your Stripe public API key. See Stripe's docs
Supported currencies: your currency as an ISO 4217 3-letter code (eg.
Automatic payment capture: If enabled, Saleor will automatically capture funds. If disabled, the funds are blocked but need to be captured manually.
Secret API key: your Stripe secret API key. See Stripe's docs
By activating Stripe integration, Saleor will automatically subscribe to Stripe's webhooks, as a result Webhook endpoint field will receive an id of the subscription which allows identifying a webhook on Stripe's dashboard side.