I have added windows phone toolkit using nuget package in windows 8.1 universal app project. it is added successfully, but I can't see reference assemblies in the project and neither i can add reference in page xaml to use toolkit controls. How can use windows toolkit in universal windows phone 8.1 app?
The Windows Phone Toolkit is currently (26th of April, 2014) only supporting Silverlight 8.0 / 8.1 applications.
If you wish to re-use components, you would need to download the source from CodePlex and port the individual components to a Windows Runtime library project. However, this might require a (very) large portion of work.