The Great Work, or main mission, of the Thelemite is to attain the Knowledge and Conversation of the Holy Guardian Angel, also known as the Higher Self, who will lead one to realize his or her True Will. This can be achieved by doing magickal rituals like Liber Samekh, meditating, and living in accordance with the Law of Thelema.
Crowley uses the spelling “magick” instead of “magic”, because he wants to differentiate Thelema’s ritual practices from stage magic. “Magick” is the process of discovering one’s true will and of causing change in conformity with that will. There is a results magic and spellcraft component to Thelemic magick, but it is based around the goal of realizing one’s will.
There are quite a few philosophical as well as ritual similarities between Thelema and Wicca, due to the spread of ideas in English occult subcultures as well as the Campbellian universality of archetypes, among other things. The wiccan Rede is “an it harm none, do as ye wilt”, which also stresses the importance of will. Thelemic god-figures are cognate with Wiccan ones; Hadit is the God and Nuit is the Goddess. Ra-Hoor-Khuit represents the individual Will, born of these opposing forces. Indeed, Thelema as well as Wicca recognizes that everyone’s soul has both masculine and feminine aspects. Thelema, being a part of the Western occult tradition, uses the Aristotelian elements, the watchtowers, and many of the same correspondences as does Wicca. Crowley actually wrote one of the earliest comprehensive tables of correspondences, called Liber 777. It is an excellent reference that shows the unity between Hindu and Buddhist, Egyptian, European occult, Jewish and Islamic spirits, herb usages, and much more. I suggest that my readers acquire a copy of 777 and supplement it with modern correspondence books that also contain information on traditions that Crowley did not research.
The most popular Thelemic group is the O.T.O., the Ordo Templi Orientis, of which Crowley used to be the leader. Although I am not a member of a group, I do believe that being involved with a group can be a valuable experience. They hold workshops, rituals, and the Gnostic Mass, which is a weekly Thelemic service that is a good alternative to a Christian Mass.
So how do you being applying Thelema to your life? Through meditation and the practice of Thelemic ceremonial magick. Thelema, being more of a mystical tradition tends to be heavy on invocation and cleansing rituals, rather than results rituals as in Chaos Magic. I will leave you with a basic rite that can be used as a part of spellcraft as well as Thelemic devotion. It is a Thelemic adaptation of the Kabbalistic Lesser Banishing Ritual of the Pentagram, and uses the Greek language as a testament to the Hellenic influence on Thelema.
Books You Might Enjoy:
Paul Boyer - The Salem Witchcraft Papers Vol 3
Simon - The Complete Simon Necronomicon
Frater Hoor - A Thelemic Calendar
Paul Foster Case - The Life Power