How can I create a login popup for discount coupons on my website?

[Mattinnovations]

Hey Everyone,

The website is: https://naturalendurance.com/ 

I'm trying to create a popup over our "collections" page: https://naturalendurance.com/collections/all  that will prompt users to create a login and receive a discount coupon (one time per person). I currently have an app that allows me to collect email subscribers but does not allow collecting actual website account logins.

Is this possible via an app or something else? I'd like to be able to customize the text/look (within reason)

Thank you!