How can I add tags to cards?

To add tags to a card, click the card to open the Card Details. Then click Tags button in the “Add properties” section of the popover window on the right.

Now type in the tag and hit Enter. 

When you click on the Tags button you can also see a list of tags already linked to cards on this board. To choose one of them, just hover over it and tick the box on the right. You can add several tags.

There is no way to edit a Tag or remove it from the list while the Tag is attached to at least one card. Once the Tag is removed from all the cards, it disappears from the list automatically.