Sorry, that's good feedback. I'll add some controls to the description now and into the build later.
In order to play the card you first click it to select it, and then if it is a card that effects one ally or enemy, you click on the ally or enemy. If it is a card that effects all enemies or allies, you can just click above the cards around the characters to play it. You can also click a card after it is selected to deselect it. Once you are out of energy you need to click end turn for the enemy turn to start.