*Note: All controls are default, and can be changed in the Settings screen
When faced with an enemy, you can draw an equipped weapon by pressing its Quickslot number, [1], [2], or [3]. Alternatively, you can press [X] to redraw your last used weapon. Press the button again to sheathe the weapon.
With a melee weapon drawn, use [LMB] for a basic attack. Melee weapons also have a heavy attack ([F]) and a special attack ([Q]). Use the heavy attack if you can't break through an opponent's blocking. The special attack varies by weapon, so experiment with how to integrate it into your combat style.
With a ranged weapon drawn, hold [RMB] to aim the weapon and press [LMB] to shoot.
To avoid incoming damage, you can attempt to dodge by pressing a direction and [SPACE] at the same time. Or, while a melee weapon is equipped, you can attempt to block the attack by holding [RMB]. Both of these come at a large cost to Stamina, and must be used carefully to avoid becoming exhausted.
Stamina is a large part of combat. Most actions cost Stamina, and once you run out you enter an exhausted state. While exhausted, your basic attack becomes weak and slow, and you cannot roll or block. Be careful to monitor your Stamina so you aren't vulnerable at the wrong moment. Making sure you are well hydrated increases the rate that Stamina regenerates, so keep your Drink meter topped off to maximize your effectiveness.
Magic and special attacks consume Mana. Mana is slow to regenerate, so be careful not to burn it too quickly.