On page 45 of the Saddhana, we have the recitation of the Mantra,
which is repeated at this point as many times as possible (hundreds or thousands of times). As we recite it, we're not just saying the words or the syllables, but we're visualizing.
We visualize the seed syllable, the essence syllable of
Green Tara, being on a lotus in our heart. That syllable is
syllable TAM. Around the syllable TAM are the(Tibetan) letters of the mantra,
going around the seed syllable in a clockwise rotation. From the rotating Mantra light rays go forth. These light rays first of all, as before, go forth and make offerings to all enlightened beings in all of the ten directions. When the light rays return, one is transformed into Green Tara. So, now you are meditating on yourself as Green Tara. You are no longer an ordinary living being, but you have attained the state in which you are undifferentiated from Green Tara. So you're visualizing yourself as (before we visualized Her in the sky in front of us) now we are, through this process of purification, of saying the mantra, transformed into Green Tara. We are therefore able to send forth these rays of light to accomplish the protection and happiness of beings.