You need to obtain the API key from Strip. Here is how you do it:
Step 1: Click on Developers > API keys in your Strip account
Step 2: Obtain the API tokens for your account:
Step 3: Go to Webhooks section
Step 4: Add new Webhook
In your Stripe setting, you get to see the webhook URL of your switch. This Webhook URL is what you need to fill in. Then, you need to select "charge.succeeded."
Step 5: Activate your key for production
In stripe, you need to activate your account. Before you do that, your API account is a test sandbox account. When your account is still in test mode, you can use the following link to get the test credit card numbers to test your setup.
When your stripe key is started with "test" keyword, that means this key is a test sandbox key instead of a production key.