I’m not sure if I can follow with what you say, so I’ll just try and give things a bit more context.
When I say place it within your pawn, I mean you should make a blueprint that inherits from the pawn you use for your demo, this will probably be the default pawn within the AR template.
If you’re unfamiliar with the use of pawns and creating blueprints, try following some tutorials, you don’t have to get into AR immediately, the basics are the same for any platform.
also try to get a grip of the framework behind a game before you get started, this might help you a lot when it comes to understanding how things happen in Unreal.
( Gameplay Framework | Unreal Engine Documentation )
*Understanding the framework, and understanding the basics of blueprints will highly increase your ability to find solutions for your own problems through searching on the forum, YouTube or other answer pages, as you will learn the correct keywords you are looking for. *
As for your CAD model, everything that is just going to be “static” in your scene, you can place within a StaticMeshActor. This is a blueprint class that inherits from Actor, and has a *StaticMeshComponent *in it. (this is the kind of actor you spawn when you drag a mesh from your content browser into the scene.
For actors you want to do stuff, or add logic (for example the “Play My Animation” function I made in the example), you create new blueprints.
The only reason to place all your meshes in a blueprint together might be to be able to have functionality that applies to everything, or to keep an overview. There’s not really a need for it in your case.