I need help...please?

Just take deep breaths and remind yourself 당신 can do it. Try not to think about the people watching, think about the emotion 당신 put into the song :)

Tell yourself 당신 can do this. and picture everyone in there underwear :3

well my mind is very very active i can imagine a robot out side the school shooting at something
.....thats just me but the best way is to think about the future just think about when your 노래 think that your a 별, 스타 and the ppl in the crowd is your 팬 :P

Have 당신 ever been on stage performing 또는 something like that?
If 당신 haven't, let me tell 당신 something, it's not frightening at all, because the light won't let 당신 see the people, so it's like 당신 and your friend are there alone and that's a plus if you're afraid/nervous to go on stage.
Another thing 당신 could do is:
-Imagine you're in your room 또는 some other place where 당신 feel calm.
-When 당신 enter on stage never look at the audience and when 당신 start singing, start with your eyes closed and, slowly, start opening them.
-Sing turned to one your 프렌즈 (e.g: If you're 4, 당신 sing turned to friend 1 and 프렌즈 2 and 3 sing turned one to another)
-If 당신 can, ask the guy who's responsible for the lights to turn off the lights for the audience 또는 something like that.

Oh my goodness. I remember when I used to have stage fright. Well here's what I can tell you.
I suggest 당신 bring the lyrics up on stage with you. Then don't look at the people out there in the crowd and just read the words.
If 당신 can't do that picture everyone in their underware. That's the best I can tell u.
Good luck with the talent show.

The important thing is to have fun. If 당신 enjoy that song and mentally at that moment live that song...it won't be like you're performing it. People will see it as real because 당신 enjoy it. Same goes with anything!