Since your credit card information is collected when your booking request is sent, your payment will be made automatically once the host accepts your booking request.
If your payment fails, you will be notified and you will be able to retry the payment from your account. If you do not retry your payment successfully within 48 hours, the booking request will expire. If you still wish to rent the RV, you will need to send a new request to the host.
For more information regarding the payment schedule, please refer to this article: How do rental payments work?