How to add "gift wrapping" option at checkout

Hi, I want to add a gift wrapping option for an additional $4 on my clients webflow site. How can I accomplish this? I was thinking of adding a check box where users can click and it will add the $4 to their cart. Unfortunately I’m not sure how I can accomplish this. Thank you

Here is my site Read-Only: Shikha's Exceptional Site
(how to share your site Read-Only link)