when you press the attack key, arrows will appear above your char, you need to press it when there are monster near of you
i did not see the attack key or which is it
never mind i found it tho the keys 1 2 3 don't work in the game
you choose controls on the char selection menu, if you choose WASD this is "H" if you choose Arrows this is "numpad 1" and if you choose a gamepad this is "A" ( xbox controller )