Attaching GameObject and ParticleSystem to C# script

I've got a script that is not a component to anything, here is the code: using UnityEngine; using System.Collections;

 public class PlayerCenter : MonoBehaviour {
 
     public ParticleSystem particles;
     public GameObject player;//these 2
 
     void Start () {
         particles.enableEmission = true;
     }
 
     public static void killPlayer(string reason){
         GameObject.Destroy(player);
         particles.transform.position = gameObject.transform.position;
         particles.Play();
         }
 }

Apart from these errors :

I also want to find a way to attach my 'player' gameobject and 'particles' particle system to the script. Here is how my project looks like:

Thanks in advance!