Okay, the in-game instructions for Caravan are more obtuse than a Legionary. I looked online for some tutorials, but they have absolutely nothing on how to actually thumb through the cards in your hand.

So how do you thumb through cards in your hand on the PC?

You'd think with the mouse, but NO, you use the cursor keys, If I remember right all other actions are displayed on screen. though to shuffle through your cards to set up your deck you use the mouse and little arrows on the side of the pack... go figure. They could have made it SO much easier and intuitive.

Took me a while to figure out, once you select a card to play, you have to get it into the right position.

You need to move the card over the relevant stack you want to play it on, and then press down, so it goes green.