Assign C++ Functions to Blueprint events

I have a UMG blueprint (let it be A) that simply inherits from UWidget (No custom C++ subclass). It resides in another UWidget (name it B) (but inherited from custom C++ subclass).
My first question is what’s the best practice to get a pointer to A from B. I’ve currently bounded its UPROPERTY (UPROPERTY(meta=(BindWidget))).

Secondly, How can I assign a C++ function to the OnClicked event of A from B.

Thanks in advance