How to install?

[dpretolesi]

Hi,

How do I install this plugin in Unity? I've put the folder into the Project Window but every time I try to generate a model I get this error:

NullReferenceException: Object reference not set to an instance of an object
LDraw.LDrawEditorWindow.GenerateModelButton () (at Assets/LDraw_Importer_Unity-master/Assets/LDraw-Importer/Editor/Scripts/UI/LDrawEditorWindow.cs:55)
LDraw.LDrawEditorWindow.OnGUI () (at Assets/LDraw_Importer_Unity-master/Assets/LDraw-Importer/Editor/Scripts/UI/LDrawEditorWindow.cs:45)
System.Reflection.MonoMethod.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at <e1319b7195c343e79b385cd3aa43f5dc>:0)
Rethrow as TargetInvocationException: Exception has been thrown by the target of an invocation.
System.Reflection.MonoMethod.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) (at <e1319b7195c343e79b385cd3aa43f5dc>:0)
System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) (at <e1319b7195c343e79b385cd3aa43f5dc>:0)
UnityEditor.HostView.Invoke (System.String methodName, System.Object obj) (at /Users/bokken/buildslave/unity/build/Editor/Mono/HostView.cs:342)
UnityEditor.HostView.Invoke (System.String methodName) (at /Users/bokken/buildslave/unity/build/Editor/Mono/HostView.cs:336)
UnityEditor.HostView.InvokeOnGUI (UnityEngine.Rect onGUIPosition, UnityEngine.Rect viewRect) (at /Users/bokken/buildslave/unity/build/Editor/Mono/HostView.cs:310)
UnityEditor.DockArea.DrawView (UnityEngine.Rect viewRect, UnityEngine.Rect dockAreaRect, System.Boolean customBorder, System.Boolean floatingWindow, System.Boolean isBottomTab) (at /Users/bokken/buildslave/unity/build/Editor/Mono/GUI/DockArea.cs:361)
UnityEditor.DockArea.OldOnGUI () (at /Users/bokken/buildslave/unity/build/Editor/Mono/GUI/DockArea.cs:320)
UnityEngine.Experimental.UIElements.IMGUIContainer.DoOnGUI (UnityEngine.Event evt, UnityEngine.Matrix4x4 worldTransform, UnityEngine.Rect clippingRect, System.Boolean isComputingLayout) (at /Users/bokken/buildslave/unity/build/Modules/UIElements/IMGUIContainer.cs:266)
UnityEngine.Experimental.UIElements.IMGUIContainer.HandleIMGUIEvent (UnityEngine.Event e, UnityEngine.Matrix4x4 worldTransform, UnityEngine.Rect clippingRect) (at /Users/bokken/buildslave/unity/build/Modules/UIElements/IMGUIContainer.cs:438)
UnityEngine.Experimental.UIElements.IMGUIContainer.HandleIMGUIEvent (UnityEngine.Event e) (at /Users/bokken/buildslave/unity/build/Modules/UIElements/IMGUIContainer.cs:421)
UnityEngine.Experimental.UIElements.IMGUIContainer.HandleEvent (UnityEngine.Experimental.UIElements.EventBase evt) (at /Users/bokken/buildslave/unity/build/Modules/UIElements/IMGUIContainer.cs:401)
UnityEngine.Experimental.UIElements.EventDispatcher.ProcessEvent (UnityEngine.Experimental.UIElements.EventBase evt, UnityEngine.Experimental.UIElements.IPanel panel) (at /Users/bokken/buildslave/unity/build/Modules/UIElements/EventDispatcher.cs:511)
UnityEngine.Experimental.UIElements.EventDispatcher.Dispatch (UnityEngine.Experimental.UIElements.EventBase evt, UnityEngine.Experimental.UIElements.IPanel panel, UnityEngine.Experimental.UIElements.DispatchMode dispatchMode) (at /Users/bokken/buildslave/unity/build/Modules/UIElements/EventDispatcher.cs:307)
UnityEngine.Experimental.UIElements.BaseVisualElementPanel.SendEvent (UnityEngine.Experimental.UIElements.EventBase e, UnityEngine.Experimental.UIElements.DispatchMode dispatchMode) (at /Users/bokken/buildslave/unity/build/Modules/UIElements/Panel.cs:176)
UnityEngine.Experimental.UIElements.UIElementsUtility.DoDispatch (UnityEngine.Experimental.UIElements.BaseVisualElementPanel panel) (at /Users/bokken/buildslave/unity/build/Modules/UIElements/UIElementsUtility.cs:245)
UnityEngine.Experimental.UIElements.UIElementsUtility.ProcessEvent (System.Int32 instanceID, System.IntPtr nativeEventPtr) (at /Users/bokken/buildslave/unity/build/Modules/UIElements/UIElementsUtility.cs:68)
UnityEngine.GUIUtility.ProcessEvent (System.Int32 instanceID, System.IntPtr nativeEventPtr) (at /Users/bokken/buildslave/unity/build/Modules/IMGUI/GUIUtility.cs:179)

Thanks in adavance for the help.