To normal attack just remove a ability or spell from your right or left click, or like someone said, move around abilities/spells and try. Because of the cooldown counter you will instead be using your normal attack until the ability is ready for use.
Like Yoshi said, normal attacks are pointless. What I really wanted to say is that I couldn't find "Normal Attack" as an icon/skill/bind in the case I wanted my wizard to swing her sword. Maybe they tucked it away since yes, you pretty much never used normal attacks once you had your primary/secondary skill