Casting a spell or doing any form of magick involves more than just saying specific words and having specific ingredients gathered together. To make it all work you have to be able to draw up and then direct energy to power the whole thing. How can you learn about magical energy, how to tap into it, and how to direct it?
Fortunately there are quite a few good books on precisely that topic!
Many handbooks on witchcraft include at least basic descriptions of how to tap into magical energy for doing spells — one that in particular that has a solid explanation is “The Inner Mysteries: Progressive Witchcraft and Connection With the Divine” (also previously published under the title “Progressive Witchcraft”) by Janet Farrar and Gavin Bone. Another that I highly recommend is “The Sorcerer’s Secrets” by Jason Miller.
Other books about magick that include a lot of good material about how to tap into and use magical energy include “Six Ways: Approaches & Entries for Practical Magic” by Aidan Wachter, “The Book of Magick Power” by Jason Augustus Newcomb, “Initiation Into Hermetics” by Franz Bardon, and “Hands-On Chaos Magic” by Andrieh Vitimus.
There are also a few good books that are about nothing but working with magical energy. Look for “Real Energy” by Phaedra & Isaac Bonewits, “Energy Essentials for Witches and Spellcasters” by Mya Om, and “The Witch’s Eight Paths of Power” by Lady Sable Aradia.
Another way to learn about magical energy and how to tap into it is to explore various martial arts and “alternative healing” methods such as yoga, Tai Chi, Qi Gong, and Reiki among others. A few books that could be helpful include “Magick of Reiki” by Christopher Penczak (who has many other books out on witchcraft as well), “Wheels of Life” by Anodea Judith, and “Taoist Cosmic Healing” by Mantak Chia (for clear how-to explanations of tapping into and manipulating Chi/Ki/Qi.)
And finally, a couple of books about using dance and motion to not only tap into magical energies, but also to shift your consciousness into altered states: “Moving Into Ecstasy” by Amoda, and “Trance Dancing with the Jinn” by Yasmin Henkesh. (Check out the Trance (Part 1) and Trance (Part 2) booklists for more about working with altered states of consciousness.)