How can I control Spawn speed/rate from an Object spawner? I'm new to Unity and scripting, and would like to delay the spawn rate of objects coming out of an ObjectPooler.

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class CubeSpawner : MonoBehaviour
{

ObjectPooler objectPooler;

private void Start()
{
    objectPooler = ObjectPooler.Instance;
}

// Update is called once per frame
void FixedUpdate ()
{
    ObjectPooler.Instance.SpawnFromPool("Cube", transform.position, Quaternion.identity);
}

}

Hi, there are many ways to do this, an easy one is to use InvokeRepeating instead of the FixedUpdate.
You can do something like this:

ObjectPooler objectPooler;
    public Float spawnRate;

    private void Start()
    {
        objectPooler = ObjectPooler.Instance;
        InvokeRepeating("Spawn", 0, spawnRate);
    }

    void Spawn()
    {
        ObjectPooler.Instance.SpawnFromPool("Cube", transform.position, Quaternion.identity);
    }