1. Click on the poof. 2. Move the mouse to where you want to move to. 3. Click. If your move hits the enemy, you will inflict damage on the enemy. Otherwise, you will move to the end of the line. This may be changed in a future update. 4. When the enemy moves, click to dodge. 5.Repeat.
This is an example of a different battle that may be in the game. The Fox has greater speed and agility than the slime, but much less health.