AR app - who do I attach something to the ar camera?

I make an ar app using the epic template. In this app there is some 3d models and 3d texts. The 3d texts appear above the models with an animation.
I want that the user don’t miss the animation. The animation start only if the user point with the smartphone to the right model.

I think the goal is very easy. Attach a hidden cube on the front of the ar camera and use Event Actor Begin Overlap (correct me if i’am wrong).

But who do i attach the cube on the camera? I can’t find it evrywere in the project.

Thanks for your help and sorry for my english.