Not a silly question!
The short answer is you can use ctrl+v (or Edit > Paste Widget in the menu) while you're looking at a card.
The slightly longer answer is this:
Decker's image data, widgets (including contraptions) and even whole cards can be copied and pasted between decks very easily.
As an example: if you copy a plain button widget and then paste it somewhere else... you get a matching button.
But if you paste it into a text editor like notepad you get something that looks a little bit like the code blocks in the contraption bazaar:
%%WGT0{"w":[{"name":"button1","type":"button","size":[60,20],"pos":[230,164]}],"d":{}}
That's because this is what widgets look like when they're stored in your system's clipboard. They start with %%WGT and contain all the information about their size and scripts and data, etc.
So Decker will know that if there's a %%WGT at the start of a string that you're pasting (that you copied from the bazaar) that means you're pasting a widget!
Just like it would recognize %%IMG as image data or %%CRD as being a whole card.
We're using the forums as a place to pass this easy kind of copy-and-paste clipboard data to each other in order to share our inventions and tools. Because it just works. :)
So, yeah, when you copy a contraption from the bazaar you can just paste it directly onto a card!
Have fun, and good luck with your finals!