I suggest you read a basic C++ object oriented tutorial.
A class member is:
class.... {
public: (or private:)
MySpawnerActor* parentSpawner; //<-- that's a class member.
}
And inside your c++ you get the instance, wherever you want. in the BeginPlay function, for example:
parentSpawner = (MySpawnerActor*)this->GetOwner();