How Do I Start Over Again?

I am trying to design our website using your free version of the theme Vantage.

Somewhere along the way, I have managed to lose the entire menu bar and generally bollocks the entire page!

I would like to just begin over again, but though I have deleted and then re=added the Vantage theme, what appears are all of the mistakes I made, rather than a pristine copy of the theme.

Can you provide me with some guidance on how I can begin again with the Vantage theme?

Many Thanks!