A weapon equipped
A weapon is your tool to attack someone, and it can help a lot. This way you need to have a weapon equipped. There are two ways to equip a weapon: one is by double-clicking it in your backpack, the other is by dragging it onto your paperdoll. Unsheathe it by using R-key. This will take you into a third person view, and it becomes a little easier to react to enemies and allies in your immediate area. To attack an enemy, run up to him and try to keep him in your crosshair while you press the left mouse button to swing against him.