like he said use the attack on the menu,
i park it on my left lower corner right under the hotbars,
you can ALSO USE F6
that toggles attack on and off!
you have in Options which is on the first left side button of the character sheet, at the bottom, and choose stuff,
like additional hotbars (1,2, or 3)
and stuff,
ok? hope that helps
good luck and thank you for playing Dark Age of Camelot