set gamobject via script in non-Monobehaviour class?

Could someone tell me how to set a Gameobject to an existing variable public GameObject propsRoot;
via another script like with scriptableobjects

The header of the class:

 using System.Collections.Generic;
 using UnityEngine;
 using UnityEngine.Serialization;
 using UnityEngine.UI;
 namespace KnifePlayerController
     public class RifleHandsController :  HandsController, IWeaponAmmo, IWeaponShootMode

If you need more Information let me know :wink:

Assume you do it in runtime, then you could use GameObject.Find