To accept payments for ticketing through credit card, go to Payment Settings under Basics and choose a payment gateway. After selecting a payment gateway viz. PayPal, Authorize.net, Stripe, enter the details as asked, and Save. These details are necessary to make sure payments are processed and you're notified of the transaction.
Please note that we do NOT charge any service fees for any payment transactions. It's between you and the payment gateway provider. You get paid directly from your payment gateway provider. Payment provider may charge you its service fees. We do not.