Lord Caitanya said:

The most astonishing thing is that this tree is not stationary. It expands and spreads throughout the entire spiritual sky, and in every leaf of that tree, Krishna enjoys His pastimes with His devotees. Even a single leaf contains millions of universes and unlimited pastimes.

However, I cannot directly provide or link to a PDF file due to copyright restrictions. Many ISKCON publications, including stories about the desire tree (the kalpa-vriksha in the spiritual sky of Goloka Vrindavana), are copyrighted by the Bhaktivedanta Book Trust (BBT).

Instead, I can offer you a from the Caitanya Caritamrita (Madhya-lila, Chapter 21) that beautifully explains the "Desire Tree" (Kaliya-krishna or Chintamani tree). You can use this story for your own notes or teaching. Story: The Wishing Tree of the Spiritual Sky Context: Lord Caitanya Mahaprabhu is teaching Sanatana Goswami about the nature of the spiritual world, Goloka Vrindavana.

“In the spiritual sky, there is a supreme planet called Goloka Vrindavana. At the center of that planet stands a transcendental tree called the — the Desire Tree. This tree is not ordinary. It is fully spiritual and conscious.