Can you help me figure out how this WP site is achieving something

Hello all,

One of the frustrating times in WP development when you see the sort of thing you’re trying to achieve but can’t for the life of you work out how it’s done.

Anyway, there is a perfect example of the sort of thing I’m trying to do here at – https://phylogame.org/cards/ which is shown when you select a card it is added to the shopping cart at the left hand side of the page. When you hit print it then opens up a print dialogue box with the cards you have selected ready to print.

If I could recreate this then I’d be very happy – but how do I do that?! Would be very grateful for any help anyone can provide!

My site is https://www.7r1n17y.com, it’s a trading card game for children (site’s not really written or finished yet but the bare bones are there).

Best wishes,

Andrew