The block of code above starting with "%%CRD0" is what a card looks like in the system clipboard. If you select and copy the entire thing from your web browser, in Decker you should be able to choose "Edit -> Paste Card" from the menu and then have the entire example to play with interactively and modify.
It might be best to tackle some simpler projects that involve scripting before diving in the deep end. There are lots of useful examples and discussions here in the community forum. In particular, it might be worth trying the examples in these tutorials to gain some familiarity with adding interactivity to decks:
Make your own Chicken Generator: https://itch.io/t/3593043/make-your-own-chicken-generator
Building a Font Importer: https://itch.io/t/3177237/building-a-font-importer
Scripting One-Liners: https://itch.io/t/2929513/scripting-one-liner