There is a bolt to loosen the clamp mechanism so you can adjust the lever, then clamp it tight again. You access the bolt from the front, under the lever. http://www.parktool.com/repair_help/lever.shtml
Carbon handlebars may not react well to twisting the levers but Al bars are fine.
When re-aligning the levers, you can fine tune the position for comfort. I prever a few degrees on cant in mine so they point in a fraction.