Please help me restore my mac

Hi there!

I have a problem with my macbookair, it has storage capacity of 80 GB. I tried to perform raid on it but I ended up deleting all the hard disks. Now when I start it starts but ends up with a picture of a folder with a question mark on it and when I start it and press and hold the option key it does not show any disk. Please help me so that it returns to its original way of working.