Using HoloToolkit-Unity in Your Project
Open or create your project in Unity.
Assets -> Import Package -> Custom Package… [Navigate to the package you exported above]. NOTE: The HoloToolkit-Examples folder (and all its content and subfolders) is optional when you import the custom package. You can uncheck it in the Import Unity Package window that shows all the contents of the package before performing the import.
You should now have a HoloToolkit menu item.
https://github.com/Microsoft/HoloToolkit-Unity/blob/master/GettingStarted.md