After instaling the package you need to add the newtonsoft.json.dll into assemble path by runing the flowing command.
Before we can use our assembly, we have to add it to the global assembly cache (GAC). Open the Visual Studio 2008 Command Prompt again (for Vista/Windows7/etc. open it as Administrator). And execute the following command. gacutil /i d:\myMethodsForSSIS\myMethodsForSSIS\bin\Release\myMethodsForSSIS.dll
flow this link for more informATION http://microsoft-ssis.blogspot.com/2011/05/referencing-custom-assembly-inside.html