Get your API keys from Stripe:
Click "Developers" → "API Keys" in the left menu item.
Make sure that you are not using test data. If this is the case, switch the View test data toggle. Test API keys will not work.
Copy the value from the Publishable key row, from the Token column. It should look like pk_live_somelongrandomvaluelikeVqFze9etc
Copy the value from the Secret key row, from the Token column. It should look like sk_live_somelongrandomvaluelike0Rx3jvetc