On Flutterwave, there is the live and test environment. The test environment is for you to look around, see how it works, and handle your integrations. When you are ready to go live and transact with real funds, you can then switch to the live environment, where you can then charge real cards, bank accounts, etc., and make real transactions.
When you login to your dashboard, there is description at the top right showing whether you're in the test or live mode.
To switch between the test and live modes, simply toggle the test mode switch shown in the image below.
NB: To get your test API keys, simply go to the API page and switch to test mode. The same applies for live keys.