One of my classes:
// Fill out your copyright notice in the Description page of Project Settings.

#include "TankPlayerController.h"



ATank* ATankPlayerController::GetControlledTank() const {
	return Cast<ATank>(GetPawn());
}

void ATankPlayerController::BeginPlay() {
	Super::BeginPlay();
	auto ControlledTank = GetControlledTank();
	if (!ControlledTank) {
		UE_LOG(LogTemp, Warning, TEXT("PlayerController not possesing a tank"));
	} else {
		UE_LOG(LogTemp, Warning, TEXT("PlayerController possessing: %s"), *ControlledTank->GetName());
	}
}

void ATankPlayerController::Tick(float deltaTime) {
	Super::Tick(deltaTime);
	AimTowardsCrosshair();
}

void ATankPlayerController::AimTowardsCrosshair() {
	if (!GetControlledTank()) { return; }

	FVector HitLocation; // Out parameter
	if (GetSightRayHitLocation(HitLocation)) {
		GetControlledTank()->AimAt(HitLocation);
	}
}

// Get world location if line-trace through cross-hair, true if it hits landscape
bool ATankPlayerController::GetSightRayHitLocation(FVector &OutHitLocation) const {
	// Find the cross-hair position
	int32 ViewportSizeX, ViewportSizeY;
	GetViewportSize(ViewportSizeX, ViewportSizeY);
	auto ScreenLocation = FVector2D(ViewportSizeX * CrossHairXLocation, ViewportSizeY * CrossHairYLocation);

	// "De-project" the screen position of the cross-hair to a world direction
	FVector LookDirection;
	if (GetLookDirection(ScreenLocation, LookDirection)) {
		GetLookVectorHitLocation(LookDirection, OutHitLocation);
	}

	// Line-trace along that look direction, and see what we hit (up to max range)
	return true;
}

bool ATankPlayerController::GetLookDirection(FVector2D ScreenLocation, FVector &LookDirection) const {
	FVector CameraWorldLocation; // To be discarded
	return DeprojectScreenPositionToWorld(ScreenLocation.X, ScreenLocation.Y, CameraWorldLocation, LookDirection);
}

bool ATankPlayerController::GetLookVectorHitLocation(FVector LookDirection, FVector &HitLocation) const {
	FHitResult HitResult;
	auto StartLocation = PlayerCameraManager->GetCameraLocation();
	auto EndLocation = StartLocation + LookDirection * LineTraceRange;
	if (GetWorld()->LineTraceSingleByChannel(HitResult, StartLocation, EndLocation, ECollisionChannel::ECC_Visibility)) {
		// Set hit location
		HitLocation = HitResult.Location;
		return true;
	}
	HitLocation = FVector(0);
	return false; // Line trace didn't succeed
}
The .h file:
// Fill out your copyright notice in the Description page of Project Settings.

#pragma once

#include "CoreMinimal.h"
#include "Tank.h"
#include "TankPlayerController.generated.h"
/**
 *
 */
UCLASS()
class TANKTOOLS_API ATankPlayerController : public APlayerController
{
	GENERATED_BODY()


private:

	ATank * GetControlledTank() const;

	virtual void BeginPlay() override;

	virtual void Tick(float deltaTime) override;

	void AimTowardsCrosshair();

	bool GetSightRayHitLocation(FVector &OutHitLocation) const;

	UPROPERTY(EditAnywhere)
	float CrossHairXLocation = 0.5;

	UPROPERTY(EditAnywhere)
	float CrossHairYLocation = 0.33333;

	UPROPERTY(EditAnywhere)
	float LineTraceRange = 1000000;

	bool GetLookDirection(FVector2D ScreenLocation, FVector &LookDirection) const;

	bool GetLookVectorHitLocation(FVector LookDirection, FVector &HitLocation) const;
};