DP brakes should be real easy to set up, some issues you may have

We don't know if these are new or old, if old, is there any corrosion on any key parts?
Is you cable routing good / are you cables in good condition?
Are you using the correct bolt for the rear brake?
There is an adjustor bolt on the left arm, have you tried using this?
Have you followed the Shimano instructions? http://techdocs.shimano.com/media/te...9830600420.pdf