You need to configure payment options on your website.
You can set up your account to accept credit cards by selecting a payment processor. A payment processor receives your money and then transfers it to your designated bank account. Click here to read more about your Payment Processing Options.
Configuring Your Account to Accept Credit Cards
You will manage the intake of your payments from Tools -> Payment Settings. To set up your payment processor, you will select your payment processor from the pull-down menu. For payment processor specifics, please check the KB article for your payment processor of choice.
You can also select cash or check and other payment options here, in conjunction with your credit card options.
Test It Out!
Make sure you configure Payment Settings before folks start signing up for your event. Once your payment processing is set up, make sure you run a transaction for testing purposes, using a real credit card.