To save a pin, you first select a pin from one of the feeds like we've done here.
You then tap on the "Save" button on the top-right.
You can edit the pin description by tapping on it.
You can then finally save the pin by selecting the board you want to save it to. You can also create a board here.
The pin has now been saved to your board.
You can speed up the process of saving a pin by tapping and holding it directly from a feed. Doing that brings up the save screen, so you can just select a board there and you're done.