How can I implement a custom actor event in level BP?

I am trying to implement a custom event that can execute in the level BPl like the “OnActorBeginOverlap” event but its not compiling.

Objective.h

#pragma once

#include "GameFramework/Actor.h"
#include "Objective.generated.h"

DECLARE_DYNAMIC_MULTICAST_DELEGATE(FObjectiveSignature);

/**
 * 
 */
UCLASS()
class AObjective : public AActor
{
	GENERATED_UCLASS_BODY()

	UPROPERTY()
	TSubobjectPtr<class UBillboardComponent> Sprite;

	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = Objective)
	FString Name;

	void BeginPlay() OVERRIDE;

	UPROPERTY(BlueprintAssignable, Category = "Game|Objective")
	FObjectiveSignature LoadActive;
};

What error it throws at you?