Hammers on the left click, concentration on the right. [concentration is an aura]
Btw if your not familiar with F hot keys, when you hover a skill you can click 'F1-F8' so you can switch back and forth between skills.
As a paladin you will have your damage skill in the left click and your aura on the right always. Leave that aura on, and you can use shift+left click to kill as well if you are having trouble.
-wvx