How do you do this? Help with prefabs.

Questions & Answers
1

I have a prefab with 300+ cubes & meshes in it. I want to add a component to these cubes and meshes since they appear not to have it.(The component is a BoxCollider.) How would I do this without going and added it individually, since that would take to much time. Can it be done through a script or does unity have like a button.

2

If your prefab is a container for these objects, then you could assign it a class to identify it as well as handle addition of any components that might not be there:

using System.Linq;
using UnityEngine;
    
public class PrefabCollectionManager : MonoBehaviour
{
    bool _isInitialized;
     
    void Update() {
        if (!_isInitialized)
            Initialize();
    }
    
    public void Initialize()
    {
        // Loop over transforms not equal to the prefab container and child transforms not
        // having the component class
        foreach (Transform t in GetComponentInChildren<Transform>().Where(t => t != transform && !t.GetComponent<YourComponentClass>()))
        {
            t.gameObject.AddComponent<YourComponentClass>();
            // any other components you need below
        }

        _isInitialized = true;
    }
}

If you have the prefab in your Hierarchy at design time, then all you need to do is add this class to it as a component. Otherwise, when you instantiate the prefab, you’ll add it then via script.

Alternatively, you could filter the Hierarchy by searching for MeshRenderer after adding the prefab to it, then select all the MeshRenderers in the prefab, and in the Inspector Add Component and choose your script. Then click Apply in the upper right portion of the Inspector, under the object name field. This will save the prefab with the new component.