I have a few ideas, hon.
First of all, congratulations

I know you were looking forward to this! Let's see if we can help...
I don't know any actualy spells, but I have a few techniques and practices for you. I had to take a course in college last year where I had to do a 45 minute presentation on something related to my course so I have a bit of practice on speaking in public. I passed btw (lol).
1) Practice. This applies both to any script, fact sheet and posture. Spend some time each day working on how you carry yourself - back and neck alignment, eyes and chin up, shoulders back, stomach in. That stuff. Do it more and more until it's a natural part of the way you move. This way you have an image of confidence and you'll start to feel better about yourself as your core muscles are trained and your energy is more free to circulate.
2) Relax. Anytime you practice, anytime you start to feel flustered, and a couple times a day. Do a light meditation to calm your breathing, heart and thoughts. Smile.
3) Stretch. This improves circulation, flexibility and confidence. Don't forget face and hand stretches, they always get overlooked.
4) When in the actual presentation, ignore any facial expressions and postures in the audience. Instead, just be aware of the stage area. Pretend there's a white light or a shield of some kind that just separates your performing area from the world outside.
I'll add more if I think of them, but these are what I learned. Good luck!