Try to identify the various emotions you think each line might reasonably express. Look up all the words you aren't certain of, and consider that some words have more than one meaning. Once you have begun to develop some personal interpretations of your role's motivation then you must start developing an acting style to convey your interpretation. Practice projecting your voice from the diaphragm until your words are loud and clear without being shouted. Opening your mouth wider than usual will also increase volume and clarity.
Memorization is very difficult for some and very easy for others.
I have found that it can help to outline the ritual in your own words, describing the actions and speeches in brief phrases. A truly top-notch Mass officer will perform from memory, but don't let the fact that you haven't yet memorized the Mass keep you from doing it publicly. An expressive and clear reading will usually top a tentative and mistake-filled attempt at recitation from memory. And much confidence can be gained through the experience of public performance. Though Crowley did provide theatrical suggestions for set design, costuming, props, and music he still left a great deal of room for creativity.