I need some advice for the prom I am so nervous!

I Need some advice for the prom I am so nervous, my prom is in early april and really i didnt want to go but my mom is making me because ALL of my other brothers and sisters went i have an attitude about it and my sister was talking to her best friend and shes not from where we live and she asked her brother which is a year older than me (im 17 hes 18) and he told my sister that he would love to take me we have seen each other before only once but that was not to long ago but anyways i think im getting excited but im so nervous i dont know how to start a conversation with somebody that i dont really know and he doesnt know anybody down here so im not just gonna leave him by his self and were going to dinner and everything!!! im so nervous i need help.