“…G-d cannot be perceived through the mind [intellect] alone. If you would know G-d, do not seek merely to prove His existence, but turn to Him with your heart; affirm your union with Him, affirm His responsiveness to prayer, pray to Him; if you actually turn to G-d … speak to Him in your heart, you will be astonished to find how close He is to you, you will feel His nearness, you will have found G-d.” 
This has become my favorite quotation; I mention it often.
As I progressed in the practice of Visualization (still workin’ on it), I came to see how perfectly Mrs. Lichtenstein’s words describe the process. She shows so well how to go beyond mere intellectual knowledge:
1 — “affirm your union…”
I once wrote about the Kotzker rebbe’s exchange with his hasid:
Hasid: “Where is G-d?”
Kotzker: “Wherever you let Him in.”
“How do you let G-d in?”
“Know G-d’s here already.”
(I hope the Kotzker doesn’t mind my addition.)
In Jewish Science terms, as in HaBaD and other branches of Hasidut, “ein od” — nothing really exists other than G-d (Jay Michaelson wrote about this, too). Our “union” with G-d is like the union of a wave with the ocean — the wave is a unique expression of an unchanging essence, never separate from its Source.
Likewise, G-d is in everything around us and in everything that happens to us.
G-d, the same unchanging essence, is in us, too, as the higher part of our own mind; our own self.
It is only left for us to know it and adjust our view of things to it.
The realization has to be experiential (through prayer, meditation, etc.).
It can begin as an intellectual idea, or could develop into one, but it ultimately has to be confirmed by personal experience.
2 — “…responsiveness to prayer…”
G-d is always responding in kind to our thoughts — in or out of prayer.
Again, in Jewish Science terms, G-d isn’t only “Ha-Sho’mei’a t’filah” (“The One Who Hears Prayer”). Jewish Science (like New Thought and Hasidut) teaches: G-d responds in kind to any thought we place before our higher Self — the Divine in us.
We might state this clearly to ourselves, or remind ourselves of it, at the start of our visualization.
If we’re sick, we needn’t ask G-d to heal us. Instead, we declare (in images or even words; even actions) that we’re already well.
The Divine responds to the image of wellness, bringing it about, even if incrementally.
As the Tzemach Tzedek (the 3rd HaBaD rebbe) said, “Tracht gut vet zein gut” (Think ‘good’ and it’ll be good).”
3 — “…pray…”
Jewish Science doesn’t emphasize liturgical, congregational prayer, but rather “affirmative” or “visualized” personal prayer. Again, it’s choosing or creating an image of the state in which we desire to be.
I wrote a large paper on Visualization as part of my MSW degree. “Image of the desired state” was an important part of it.
(At the same time, I found Jewish Science teaching could underlie liturgical prayer, too:
One Yom Kippur, eyes closed, I visualized joy while hearing the Shofar blown. I felt darkness in me begin to vibrate, then shatter.)
So, Mrs. Lichtenstein is telling us: Know (or recall) that your very existence is an expression of G-d’s existence; this all-pervasive existence is always responding in kind to every thought you have; therefore choose a thought (mental image) of the state in which you desire to be and allow the Divine to begin to create it.
In my own experience, I’d also add that “turn to G-d (in prayer)” has meant recognizing while visualizing that it isn’t my own mind, or my mental image, that is producing the result.
The Infinite in us reaches out to its Source, as Rabbi Lichtenstein writes about “faith.”
The Divine responds.
“Visualizing” means observing it happening. Letting it happen, not making it happen. Knowing that it is happening now. Many times, I’ve ended visualized prayer not only with the desired outcome, but with an intensified feeling of G-d in and around me, too — even in unexpected surroundings.
We can be in Gan Eden in The South Bronx, too!
Just as Mrs. Lichtenstein says: “…you will feel His nearness…”
We might desire, for example, better social relations with those around us. While we should certainly strive for this ourselves, I think Tehillah would have added that try as we might, we must invoke Divine help to accomplish it. This is best done through visualized prayer.
Similarly, praying for peace in the Middle East and other areas of the world suggested to me the design:
See the peace we want as here, now. See it in detail. Feel it. Let it become more real to you than the evidence of the senses. Let the Divine express itself in and through you and everyone else, everywhere, as Peace.
For all the details I’ve mentioned about Visualization, or Visualized Prayer, it should be remembered how uncomplicated it is, too. Yes, there are some steps to proceed through, as we develop our skill. At first, a positive visual image is enough. Later, we can add the additional steps, additional understanding and some gradual (“fractional”) relaxation as an introduction, as we find them useful. But the overall simplicity of visualizing shouldn’t be forgotten. It reminds me of a yogic teaching about progressing from “dharana” (concentration) to “dhyana” (meditation): At first, our attention might be rough, but with practice, it gradually comes to flow as smoothly as oil poured from one pot to another.
That characterizes visualization, too. At first, you might think about each step. Eventually, they flow effortlessly from one to the next, and our attention stays effortlessly on the mental image we’ve chosen.
Mrs. Lichtenstein’s whole intention is to tell us how uncomplicated this is.
It’s so important that Tehillah’s work, and the Rabbi’s, be available for coming generations.
 Mrs. Tehillah Lichtenstein; Applied Judaism; [“Can We Prove That G-d Exists?” (essay)]; p. 96;
(originally part of “How Shall We Find G-d? (essay);” The Jewish Science Interpreter (magazine/newsletter), June, 1940; p. 4)