Level sequence spawned attach to other actor or component

I want to get actor which spwaned by the level sequence.
I have tried Rebinding,spawnable,etc.
I want to attch the actor(Camera Root,FXRoot),attch to character’s skeletal mesh in a custom bone/socket.
Find Actor By Tag is not useful for me.
I really want to know how to do deal with in a most offcial function?
Thanks a lot

after cast is null ?