upgrade destroyed my site. how restore wpbackup?

Newbie here.

All has been fine until I upgraded to latest wp2.9.1rc by using simplescripts on bluehost.

Btw, all was better before I upgraded to 2.9, then I thought, well, they’ll fix it with the next update, 2.9.1 beta which I upgraded to with no problems using simplescripts on bluehost.

So I thought it would work the same way again with the new upgrade, but it destroyed my site, instead of upgrading it created a new one.

I have a backup created by wpbackup emailed to me. But do not have a clue how to restore it.

Have looked for the answer but am totally confused which way to go about it.

Any helpful guidance is certainly appreciated!