Change Pickup key

Hey everybody :) I have a little problem that i cant solve... Im not really in to C# but i got a pickup script that picks up the object with mouseclick. How can i change it so you pick it up with the key E?.This might be a noobie question but im not in to C# can someone help me please:)

using System.Collections; public class Pickup : MonoBehaviour { public enum Item { Flashlight, Battery } public float Distance = 5.0f; public Item item; public AudioClip flashlightSound; public AudioClip batterySound; void OnMouseDown() { var playerPos = GameObject.FindGameObjectWithTag("Player").transform.position; if(Vector3.Distance(playerPos, transform.position) <= Distance) { if(item == Item.Flashlight) { Flashlight.HeadLightMount.SetActiveRecursively(true); Flashlight.HeadLightMount.active = true; AudioSource.PlayClipAtPoint(flashlightSound, transform.position, 1); HUD.HasFlashlight = true; } else HUD.BatteryCount++; AudioSource.PlayClipAtPoint(batterySound, transform.position, 1); Destroy(gameObject); } } }