In order to accept Stripe payments, you need to connect your Stripe account using an API key. Stripe requires both a Secret and a Public key.

To obtain a Stripe API key, log in to your Stripe account on stripe.com. From there, select Developer in the top right corner and API keys from the available tabs toward the top of the screen. In the top right-hand corner, switch from Test Mode to Live Mode. In the center of the screen, you will find the necessary keys.

More information on Stripe API keys can be found here.