Be sure the cable is routed and attached correctly at the derailleur. When you push the brake lever to the side it should pull cable.
Find the instructions for derailleur adjustments at the Park Tool site: http://www.parktool.com.
Follow the instructions precisely, do each step in proper order leaving nothing out.
If you still have problems come back here.
Are the shifters new or used? Have you used them successfully before?

Al