Homing Missile Target Indicator

I am trying to make a spaceship shooter game. I have developed a homing missile, but I am not sure how to:
A. Indicate to the player which enemy they will be shooting at ( I want to make a targeting triangle that will automatically move to the nearest enemy in the player’s vision/ where they can see)
B. Make sure that the homing missile follows where the player wants it to go

If you have the nearest enemy or target, then aiming toward it is simple:

For the direction:

 Vector3 direction = (targetPosition - playerPosition).normalized;

Then multiply that with a distance modifier:

 float distanceModifier = 1;  //adjust this to how far away from your player the arrow should be
 Vector3 arrowOffset = direction * distanceModifier; 

Then add that do your player’s position and move the arrow there.

 Vector3 arrowPosition = arrowOffset + playerPosition;
 arrow.transform.position = arrowPosition;

Finally, rotate the arrow to that same direction

 arrow.transform.rotation = Quaternion. Euler(direction);

As for your projectile trajectory, I would recommend this excellent tutorial by Tarodev:

@rysan007
Thank you so much for your advice. I am relatively new to unity, so could you give me a more in-dept explanation on what I have to do and how the code works.
Thanks,
ChocolateFudgeCake