beginner questions about theme

I’m really new to this and i need to create a web page as soon as possible for my business. I bought the theme in ThemeForest and I was hoping that i would get the template exactly as it is show in the demo, but in fact when I install it it is just a grey space.

My question is: how do I do to get my web page exactly as it is show in the demo when I bought it?

Sorry for my English, and thanks for your time.