Howdy Li!
If you’re talking about Event Tickets Plus then the checkout process and beyond is not actually handled by our plugin, it’s handled by the Ecommerce store you have setup. Do you know which one you’re using, perhaps WooCommerce? Technically what you’re looking for is help modifying the third party checkout process and so we won’t be the true experts on that, but if you let me know what you’re using I bet I can get your some more detailed instructions for swapping things around.
Cheers!
– Brook