He moves about becoming manifold within the heart where the arteries meet, like spokes fastened to the nave. Meditate on the Self as Om! Hail to you, that you may cross beyond (the sea of) darkness!

In plain words: The Self lives in the heart, where the body's channels meet like spokes in the center of a wheel, and it shows up in many forms. Meditate on the Self using the sound Om. The teacher wishes you well as you cross over the darkness.