Swinging sign

How to make the sign swing slightly on the bracket?

Should mesh 2 be a child of mesh 1?

Depends on application.

Easiest way is via material.
More complex way is via PHAT and physics.

As I understand constrait is an easy way. I looked at some tutorials and did exactly the same as these guys, but nothing happens: the mesh does not rotate.
For example: UE4 How to - Mechanical Joints with Physics Constraints in Unreal Engine 4 Tutorial - YouTube
In this guide, in the 8th minute, the man shows my situation. I can’t understand what I’m missing.

I am not understanding this information. Please could you give me a link to any tutorial?