Once the HoloToolkit Package is installed, the HoloToolkit option will appear in the main menu item of the Unity Editor. Navigate to HoloToolkit| Configure and select Apply HoloLens Scene Settings and Apply HoloLens Project Settings to apply standard settings for the holographic application within editor.

Unity will ask for a reload, and you should go ahead and do that.

In case you have to do it manually rather than by selecting Configure options, navigate to Build & Settings options from the File menu and set the properties in the Build Settings window.