Stand in front of a mirror and apply makeup. As you apply, stop after each step and write it down. Try to be as specific as possible without getting into so much detail that the meaning is lost. Continue until you have gone through the process!
Good idea to appeal to the male audience as well! If your instructor would appreciate a humorous approach, you could demonstrate how NOT to apply makeup and show photos of people, or have a model such as a wig head form on which to demonstrate. There will probably some of the males who will recognize a former date in these demonstrations and laugh. (Think of a Saturday Night Live skit)
This topic is mostly going to appeal to the girls in your class. If you have about half girls and half boys (or really, any boys at all), you might want to consider how you can tap into your entire audience.
One thing I would encourage you to think about is appealing to the men in your audience at the very beginning by saying something like, "Gentlemen, do not tune me out, you are about to learn one of the mysteries of womanhood..." or even appeal to them as future father's who might one day find themselves a single dad of daughters. Also, because applying makeup is something that is already univerally known, to make this speech more informative and less repetitive, you could include "tips" on how certain applications/colors enhance certain features, etc. Almost every women's magazine includes this kind of article, monthly, but usually just focuses on one aspect of makeup, like "lips." It would be neat to hear and see how it all can come together.
Sounds like a fun speech. Enjoy it.
An outline for a speech is fairly simple once you decide what your 2 or 3 points are going to be. "How to do makeup" is a bit broad, but here are some ideas.
If you're speaking only about how to apply makeup, your points will be in chronological order--the order in which you would apply each element. For example:
II. Applying foundation
A. Start with a clean face
B. Begin at the forehead (or wherever)
III. Applying eye makeup
IV. Applying blush
For each of these points, or whatever other points you might choose, simply list the steps as you normally do them, including any tips or advice you'd like to give along the way.
If you're covering more than just how to apply makeup, perhaps you should consider something more like this: Types of makeup, Applying makeup, Removing makeup. It really doesn't matter what you choose--though your teacher may certainly have given you more instruction, and that's what you should follow, of course. Just select those major points and start filling in the gaps. This should be much easier than some other topic because it's one you're probably somewhat familiar with, at least.
Once you've written the outline, think of creative ways to begin and end your presentation. Perhaps something funny or practical or surprising would work for this topic. (Do you know what many brands of makeup have in them?!? Quite shocking, some of them.)
The key to this speech, I think, is to start with what you know and then fill in the blanks. I wish you all the best on your presentation!