You need to have a weapon equipped when it comes to attack someone. There are two ways for you to equip your weapons: one is by double-clicking it in your backpack; the other is by dragging it onto your paperdoll. Once it is equipped, you can use the R-key to unsheathe it. By doing so, oy will be in the third person view, and this makes it easier to react to enemies and allies in your immediate area. If you want to attack an enemy, what you need to do is to run up to him and try to keep him in your crosshair when you press the left mouse button to swing against him.
Players tend to wear heavy armor to protect them from hurting. And there is an increase of your Armored Combat skill when you attack someone in heavy armor. However, wearing them comes to have some consequences. You will get a penalty to attack enemies with them, but the penalty for your armored combat skill is reduced when your this ability rises. You need to find a balanced point.
There is a tricky for attacking someone. The best way is to attack someone from behind. In darkfall online, both players and monsters gain a significant damage bonus by hitting someone from behind. You should try your best to attack someone from behind; at the same time avoid to be attack from behind.