You create cards by clicking... anywhere on the screen. If there's space, you can create a card. There's several things you can do to cards itself. You can add images (which also works on mobile, btw), paste an image URL, and more. Important to note that on the free version of Kinopio, images can not exceed 5MB. If it does, feel free to refer to my favourite image optimiser.
These "connections" that I mentioned earlier, can hold different meanings. You can set colours for the different connection, each meaning something else. So in the GIF above, say I categorised that purple connection line as "music", so everywhere I see a purple line on my board, I'll know it's referring to music. But you can create a different board altogether for different categories-- the world (or Internet) is your oyster. And yes, a card can have multiple connections.
Other features include adding filters, making each card have a checkbox so you can treat it as an item on a to-do list, use templates, and so on.
So, what can you do with Kinopio? Whatever you'd like.