I think the problem is straightforward. Do you have provided input library boost_serialization-vc120-mt-gd-1_56.lib in the Linker->Input->Additional Dependencies option. You need to put your lib in there. Please make sure. You can get help from the following snap shot - 
The snap shot above will help you to find the option from Visual Studio. Just go to project properties then you will see something like this. Go to Linker->Input and provide the required libs in Additional Dependencies. Then you are done.
EDIT:
As Sehe mentioned lib inputs are automatically handled by boost using #pragma lib. If you are using this, you just need to set the Library Directories. Library Directories can be set by going to Project Properties. If you go to Project Property you will find a tab named VC++ Directories and if you click on the tab you will find Library Directories option along with other directory options. The following figure may help you on this -

You just need to put the library directory of the boost library there.